I really like the Dave Brown mounts (round one). I also like the DuBro, but it takes up more space behind the engine. I had to recess the firewall on the L-4 for that mount to work, and even if the mount comes right to the edge of the firewall, with the cowl in place it won't be seen. I did not drop the thrust line, as I was trying to maintain a very scale appearance; since the boot cowl slopes down a little along the top, recessing the firewall actually gave me a little more room at the top of the firewall.

As far as the LHS guy goes, it clearly says on the kit box the recommended range for the plane, and I've found that the mfg generally knows pretty well what will fly their model. He's correct that the .65 is close to the .46 in power, but we're talking peak power at WOT, not real world midrange running, which is what you'd be doing most of the time; plus, the .65 would turn a larger diameter prop (scale for the 1/5 Cub is a 14 incher) and the .65 would do a better job IMO, than the 2-stroke. I wonder if the LHS would let you return it if you haven't run it yet? That is, if you really want to, it's really not a big deal. I'm just a dyed-in-the-wool 4-stroker and am prejudiced in their favor. I like the way they perform, and for my own wants they are the perfect engine.