How to remove Hyper-v from a Windows 7 machine

For that load, probably not a problem. On a system with many guests maxed out on capacity where contention is an issue, this is almost certainly not a "best practice".

I reckon MS does not consider the requirement for a dedicated adapter significant because most system boards come with dual adapters. And network adapter cards are inexpensive. (Available slots are more expensive than network adapters).

The real issue is you are off the reservation with this setup. If there were some weird problem with no documented solution, MS support would probably recommend that you install a dedicated adapter. If you have a spare slot, I would not have too much anxiety. Reconfiguring the network is not that involved.

It could be worse. Try getting it to work with a wireless adapter. Not supported (not sure about R2 but in 2008 it is not). I made it work anyway. The interesting thing is the final solution was trivial, but there are a lot of planet crackpot articles on how to make it work.

The hotfix in Microsoft KB2263829 might solve this problem.