Yes, the manual for the RV-4 says that VNE is 210. I think that Dave is extremely careful when going faster than that. One thing is that I think Van's is slightly conservative (probably with good reason) and that it is generally considered by some people that the RV is overbuilt. The only two people I have seen fly it are Dave and his wife while he was in the backseat. I don't know what speed he normally cruises at when alone but when flying with a group of "normal" RV's I am sure matches their speed. Keep in mind that this extra speed is most likely why he added a counterbalance weight to the rudder.
As far as the speed increse with the turtleback mod, he did that along with some other mods so was unable to determine an exact number, if I recall this correctly.
One other thing, a friend of mine who has ridden in the plane says that it gets quite warm in there, even with the tinted canopy, since the cabin air apparently comes through the engine compartment first.
P.S. Thanks Dave for offering to clear up some of the info sheet stuff. The stuff over my head more relates to the use of the mathmatical formulas and such. I didn't go to engineering school or anything like that