I've got a 180hp -4 with a fixed pitch Sensenich. (BTW, the Sensenich people are GREAT! Right up there with the FBO at Raton, N.M., but that's another story)
I'll put 220 pounders in the rear pit, with no problem. I haven't noticed any pitch sensitivity, but taxiing is really different! It took a few flights to remember to leave the tailwheel on the ground a bit longer on takeoff...
Unrelated to CG really, but I carry about 5 additional knots on landing also with a load in the rear pit. The RV acts more like a Piper than a Cessna when it gets slow. It will mush rapidly rather than pitch over if you get slow, and that's confirmed by not only my experience but the 3 no power landings I've been privy to, the last one this weekend at my local airport (RV8). Having said that, it WILL stall and pitch over if she's mistreated!!! In the words of our master and hero, Richard Vangrunsven, "DON'T STALL, DON'T STALL, DON'T STALL!!!"
In the end, Smokey is right...only lithe, attractive, wealthy, (ok, I added that one) girlfriends.
Jeff
Toucan N605RV