How do I (safely) upgrade Mountain Lion to Mavericks in a triple boot setup?

Question

When I purchased this refurbished 2011 Mac mini in late April, I wanted to set it up where I could have Mountain Lion, Snow Leopard, and Windows 7 in a triple-boot setup.  Knowing that the hybrid MBR setup limits the hard drive to three partitions, I had to get rid of the recovery partition.  Somehow I was able to make or keep both a .dmg file of the recovery partition and InstallESD.dmg and to clone these to a USB flash drive.  I eliminated the recovery partition, shrunk the Mountain Lion partition, added the Boot Camp partition, and made room for the Snow Leopard partition by further shrinking the Mountain Lion partition.  This setup has been working well for me so far.
The discussions I'm seeing about people having trouble with the Mavericks installer wanting to create a recovery partition make me nervous.  I don't have an immediate need to upgrade to Mavericks (I use Windows 7 and Snow Leopard more than Mountain Lion), but I would like my third OS to be the most up-to-date version available, especially since Mavericks is free.  I'll be making extensive backups of all three partitions on a larger external hard disk I'm putting together tomorrow, so I'll be able to restore everything if I mess something up, but I'd rather go into the process with a fair amount of confidence that it's likely to work without too much tinkering.
Any hints?

Answer 1

The 2010 Mac mini came with Core 2 Duo processors; the 2011 Mac mini had options of Core i5 and Core i7 processors.  My Mac mini is booted into Windows 7 at the moment; the Computer window shows that I have an Intel Core i5-2520M processor running at 2.50 GHz.  This is the model that came with the discrete AMD graphics processor.  The 2011 Mac mini and 10.7 Lion were introduced at the same event; it is highly likely that later versions of 10.6 Snow Leopard included drivers for the new Mac mini in the event that Lion wasn't ready in time.  (The similarities of the 2011 Mac mini to MacBook Pro models released before Lion may also be a factor in Snow Leopard running successfully on the Mac mini.)
I expected to have to go through extra steps to get Snow Leopard running on my Mac mini, but as long as I installed it and updated it to the latest version by using my MacBook to access the Mac mini's hard disk in Target Disk Mode, it ran just fine.  In fact, one of the first things I did with the Mac mini was the opposite:  I booted the MacBook in Target Disk Mode to see if the Mac mini could boot from the 10.6.8 installation on my MacBook's hard disk, and it worked fine.  I'm sure there are people who have had difficulties installing Snow Leopard on a 2011 Mac mini (with or without a separate Mac that officially supports Snow Leopard), but I guess I lucked out.
The main PowerPC application that I like to run every now and then is Spaceward Ho!, a strategy game that harkens back to the days of the classic Mac OS (I've been using Macs for twenty years, back to the days of the 68040 processor).  The developer of Spaceward Ho! for the iPad has tweeted that it may release an updated version for Intel Macs, but I don't know that it will maintain the "feel" of the classic version.
I recently decided to try the iDVD '06 that came with my MacBook on my Mac mini, and while it's not a PowerPC application, it won't run on Mavericks, so I have to keep Snow Leopard for that purpose.  Mainly it's just been a matter of preference:  Snow Leopard just feels more nimble than the more recent releases, and it gives me better control over when I save my files (or copies of them).
Also a matter of preference:  if I'm running a Windows application, I want to be in Windows.  If I'm running a Mac application, I want to be in OS X.  I also want all of my resources devoted to the OS I'm running at the current time, not divided between both.  I may try virtualization again somewhere down the line, but right now I'm happy enough with Boot Camp.