RE: RV-4 or Ultra Sport 40+
For a warbird "trainer" I would reccomend the UltraSport. I have had both the US and the RV. The RV is a nice sport plane and slows quite well upon landing. The US on the other hand has a higher wing loading and comes in for landing much faster. If you show it up too much, you end up with a tip-stall. BUT the US has weak main gear.