I’ve given two RV4’s a “tall man” mod, my first one that I didn’t build, and the one I have now, that I also didn’t build. I moved the roll bar/seat back support aft 2.75”, and the seat bottom piano hinge support aft 1.75”. This gives me a little more tilt, which is comfortable for me. I am 6’2” and have a 32” inseam, so I’m a little long waisted. Doing this requires some structural changes, and they are briefly outlined in the build plans that came with the kit. The sidewall support has to be modified to allow a load path for the moved roll bar. The canopy cross brace also must be moved aft by the same amount as the roll bar - 2.75” in my case. For me, this is a very comfortable cockpit now and I have more room between me and the instrument panel. Comfort for the back seater wasn’t good before the mod and less so now. My wife doesn’t like the back seat of any tandem airplane, so for me, it doesn’t matter. My grandkids love it. The rear stick did interfere with the front seatback in the full nose down position, so I just removed the stick - at first. When I did my first condition inspection, I discovered that the builder had built the elevator control stop 6* too far nose down. Nose up was fine. I rebuilt the control stop and now the rear stick doesn’t interfere, although it’s close at 1/2”. The other thing that drove my decision to do this had to do with weight and balance. My empty weight is 981#. With me in the front, 15 pounds of tool bag, etc in the bag bin, and almost full fuel (30gal), I have enough useful load for my 125# wife and nothing else to stay within my 1500# designed GW. All of this is fine with me. I seldom take anyone flying with me, and when I do, it’s a short local flight, so no need for a lot of fuel. CG has to be minded any time there is a back seater or baggage. This airplane was never designed to be a cross country airplane for two people and luggage. That airplane is the RV8.