OK, so, I'm using a V2/Mode Four rig, but it's a pain in the ass to get to our practice space, which is furnished, with, among others, Marshall 1960A's. Now, as I'm sure many are aware, the Randall is rated at the following:
400 watts @ 2 ohms
400 watts @ 4 ohms
280 watts @ 8 ohms
and no mention is made of 16 ohms. The Marshall cab, meanwhile, handles:
300 watts @ 4 ohms
2x150 watts @ 8 ohms stereo
300 watts @ 16 ohms.
Question basically is, assuming for running the amp at around half, am I going to risk any damage to the rental cab, or will I be fine?
You'll be fine. I recorded my 6505 (120W) through a greenback-laden cabinet rated at 50W. As long as you don't push them to ridiculous you'll be fine.
Far more importantly, Mode Four AND a V2? What the fuck, dude?