That's a tough tow. We've done it and really love Shaver Lake, but it's not an easy tow at all. Last summer a friend in our group did it in his moho and hated it so much that he sold the moho when he got home and bought a new pickup and fifth wheel.
Getting up the hill is a lot of work, but pretty much everyone is going slow. Coming back down is hard work though. I have integrated engine braking and an amazing tow/haul mode in my transmission and it was still work.
The problem wasn't necessarily the steepness of the grades but the length of the steep grade. Going over the Conejo Pass in T.O. is pretty short and quick. No big deal.
If your brakes aren't heavy duty and your transmission doesn't have a good tow/haul mode, then I would think twice.
We have friends in our group who won't go to Shaver because of the grade.
It's do-able, but not fun.
