Netsh store=persistent resets on reboot

Question

I am running Windows 7 with a WiFi connection to my router, and I'm connecting a Raspberry Pi via an Ethernet cable. Network sharing is turned on, and to some extent this setup works. I can ping any location (e.g. bing.com) from the Pi. I can open a web
browser on the Pi to google.com. 
However, the web brower won't connect to most sites, most of the time. I set up a packet sniffer on the PC and found that in each case that's because the PC is receiving packets of 1500 bytes, and does not pass them on to the PI over the Ethernet cable.
It sends back an ICMP Packet Undeliverable (Packet too large) message in each case. The message is sent by the PC, not by the Pi via the PC.
I ran 
netsh interface ipv4 show subinterfaces
and found that the Ethernet interface is set to MTU size 1300, while the WiFi interface is set to 1500. So I ran
netsh interface ipv4 set subinterface "Local Area Connection" mtu=1500 store=persistent
which corrected the problem.
However, when I restarted the PC, the MTU size had reset back to 1300. From reading the documentation about the netsh command, that's not supposed to happen. I
have to assume that something else is resetting the size on reboot, but I haven't been able to track down the culprit. I also have not found any way to prevent the size from being changed, by, e.g. setting an access control on the key value. (For that I'd
have to know where to find the key value.)
The Ethernet NIC is a REALTEK PCIe FE Family Controller, and I've updated the driver to the latest on the Realtek site.
I've noticed that others have asked about store=persistent settings getting lost on reboot, as far back as 2010. I'm hoping that this question might finally get answered.

Answer 1

Nope, no jumbo frames. I checked again and again because so many people were saying it was there.
I did manage to fix the issue by editing the registry. Apparently the netsh command doesn't update the registry (I actually searched for any occurrences of 1500 to see if it did), and on reboot the values stored in the registry are recopied out to wherever
they are kept for the running system.
I found instructions for locating the correct place in the registry here:
cbfive.com/blog/post/How-to-Find-a-Network-Adapter-in-the-Registry.aspx
Once I followed those instructions I updated the value stored for MTU size, and after that the PC remembered the setting over a restart.
I don't know what might happen if I re-installed the NIC's driver. Likely it would reset the MTU size to 1300, and I'd have to re-edit the registry.
Just what the store=persistent parameter actually does is a bit unclear at this point (maybe it works for some settings but not for this one, or it doesn't work for this NIC, but it would work for other NICs), but since I got things working I'll let that
be someone else's mystery. ^_^