Perry? Could you provide a link to a picture of a Perry RNV? I don't do ebay...so far! I've seen the "new" Fox RNV and don't want any...big, heavy, and expensive.
The first RNV I tried was one from an OS Max III .29R. The response was slow and not linear...like the NV was bent or something. On down the road 40 years or so, I ran a .25LA on a Skyray, and didn't like it, either. I'd choke the venturi and draw fuel in, but then it'd run right back to the tank, apparently from air leakage in the RNV. If you used an electric finger like the R/C guys mostly do, you wouldn't notice, tho. So I converted it to front NV. Much easier to get to start and keep running, because the fuel hose didn't drain back to the tank.
The RNV units that come with some Magnum engines have very nice thread fits, and while I haven't run one of these, I think they're pretty good stuff. I mounted them on other engines, specifically two MECOA .28's I gave to Glenn Reach for his youth program. Mounted the NVs so they were parallel to the cylinder, in order to protect them from breakage. Haven't heard a word from Glenn about how that worked out...but I'm hoping to see him in Edmonton in another few weeks. If you're interested in using a RNV setup, I'd suggest the ones from Magnum/ASP engines...maybe Evolution also...they look very similar, and they may come from the same factory in PRC.
Steve