Flying along in the base of the cloud is a crap idea at the best of times but coupled with rising ground and turbulence (given the wind and terrain) it is even more stupid.
Inadvertant IMC in an R22 is not a clever thing to do but a slight updraught when you are scudding along at the cloud base could cause exactly that.
What are your chances of seeing and avoiding other traffic even though you are legally COCISOS? What about someone letting down through cloud on a radar or procedural service (or some made-up procedure using GPS)- you're not going to get much warning of their arrival.
The GA answer will be that it is legal and you are trying to keep to the 500' rule rather than illegally low fly - what about turning round and going home or landing at an alternate site?
As another poster highlighted - this sort of flight profile often leads to a statistic.