Yes it does fit, the stock receiver is about the same size of the SR3100.
Personally run the DSM SR3500 at the moment.
But i will be trying to get a SR300 or SR3001 for it, its the same size if not bigger than the SR3500 and fits fine also.
yeah the miniZ looks limited but is not limited in parts.
http://www.atomicmods.com/
Check these guys out they locally in my area the live and breath MiniZ.
It has as many option parts as a regular RC. They can be as fast as a 18th scale onroad.
Its just all the parts are made for MiniZ and just MiniZ cant use it on anything else.
I was debating myself to get one or not
but i ended up with the RC18B earlier this week
and i dont regret getting the RC18B,
it can be driven anywhere outside inside on grass.