Not Enough Free Space on NetBoot Image Partition

Question

Since the NetBoot server isn't all that popular, I'm going to explain how it works a bit before I get into my problem.
I assume everyone knows how it works on the client end. You choose an image and your Mac boots that image over the network. Quick, easy, painless. It's a cool system. So on the server/admin side…
Every version of OS X Server comes with it's own System Imaging Utility. So lets say you want to make a netboot image with some utilities on it. So you take an external hard drive. Make two partitions on it. On one partition, you set it up to be the netboot image. So you install all of the utilities you want installed. You configure all of the preferences just the way you want them. Set your background image, etc, etc. On the other image, you just do a quick clean plain installation of your OS. And you also install your OS X Server Admin tools (or in case of 10.8, the Server app). So once your image-to-be is configured, you boot the second partition, and run the imaging utility. This utility will turn your volume into a netboot image. A netboot image is basically just a folder with some .plists in it, a read-only disk image of your initial volume, and a kernel or two (10.5).
NetBoot images are read-only. So when you boot them, you can make as many changes as you want. But once you shut down, all changes are lost. Every time any mac boots a netboot image, it is booting the image exactly as it was when you made it. The changes you make are stored in shadow files on the server that you can periodically toss, since they are only used during the current active session. Once you reboot, the shadow files are useless.
So here is the problem: When you make a netboot image from a real volume, the utility only leaves a small amount of free space on the volume. Even though the disk image is read only, the amount of free space matters because that's still all you get to use. In other words, if the .dmg file in the netboot image i just made only has 900 MB of free space in the volume, then that's all I get for free space on any machine I boot off that image. Even though the image is read only, and all of the "free space" is actually being stored as shadow files on the server, that limit is still applied. And 900 MB is not very much free space. So you can boot a utilities volume and if a program eats up a lot of ram, that virtual memory can eat up what little free HD space you have, and suddenly your netboot image is not very functional.
Now being the clever fellow that I am, I came up with a solution to this problem last time around. I used the following command to resize the partition (and only the partition) of the .dmg file, inside the netboot image (netboot images are just folders).
hdiutil resize -size 60g -partitiononly NetBoot.dmg
This resized the volumes to 60 GB. But it was all blank space, so the .dmg file's size did not change. It would just mount as a read only volume with 40 GB of free space instead of a few hundred MB. This little trick worked very well. But it's not working any more. I can't figure out why. But every time I try to run this command on the .dmg file, I get an error very similar to the following:
hdiutil: resize request 125829120 is above maximum size 18005952 allowed.
hdiutil: resize: failed. Invalid argument (22)
I get this error while running 10.8, 10.7, or 10.6. I get this error whether I'm trying to resize an image containing 10.8, 10.7, 10.6, 10.5, 10.4 or 10.3. I get this error whether I convert the image to a read/write image first, or even a spare image first. I get this error whether the original hard drive that volumes were on, is partitioned as APM or GUID.
The "maximum size" listed in the error message is different for each image I try to resize. It's as if the tool is trying to fit the increase volume inside the existing free space of the image's volume. Which isn't what I'm trying to do at all.
I've been using netboot images filled with utilities for years now. And overall it works very very well. I started back when the first macbooks came out with no firewire. I quickly realized I needed a better solution than booting my Mac into firewire mode to repair other Macs. And then when I got into it, I realized I could host images of all different OS versions. So now I can plug my MBP into a client's network, and boot any Mac they have off of a utility volume of any version of Mac OS X needed, all the way down to 10.3, all at the same time. And I also have NetInstall volumes too that let me install OS X for all these versions as well. The only real quirk I've had over the years, is this 'free' space issue. In the past (before the last time I updated my images, where I used the command above to resize the partitions and solve the problem), what I've done when I've ran into a HD pinch while working, is to immediately start deleting apps I don't think I'm going to need, right off the netbooted Mac. This frees up space on the netboot volume and the system is happy. And again it's all read only, so I'm not actually making changes to the image itself. One real half assed solution I thought of was to set up all of my netboot volumes as having a 1 GB file in their trash and not emptying it before creating a netboot image from the volume. Then when this problem came up and the OS was running out of disk space, I could just empty the trash. I'm quite sure this little trick would have worked, but it's so half-assed. I'd much rather just have more free space on the mounted disk images.

Answer 1

But how did my command work so perfectly last time? Here's an image. On the left, the info window of the disk image inside my 10.7 Utilities netboot image. On the right, the info window for that disk image's mounted volume. The file is only 7 GB and the volume is a 30 GB volume with ~23 GB free. None of the free space of the volume is using up any actual disk space in the .dmg file. I did this once, there's got to be a way to reproduce this again?
Here's the same thing with my 10.6 Utilities netboot image. Also in case I'm not being clear, these netboot images these screen shots are of, are from the last time I updated my netboot images ~11 months ago. These are not my current batch that I'm trying to finalize.