Hi Gang: Just a couple of comments to possibly help. I flew mine again in a Demonstration flight just this past weekend. It was an AMA Showteam act demonstrating the Golden Age of Air Racing, and we had a big crowd of spectators. Done correctly, it can really be a crowd pleaser, but I'm always fortunate enough to be able to do it off of pavement, and I can see where grass could really be a problem. So Think pavement !
Secondly, remember that it uses a fiberglass fuselage, cowl, and wheel pants, which results in a high wing loading. If you load it up additionally with a big heavy engine, you are going to even increase that wing loading. I fly mine with a Thunder Tiger Pro .46; surprised ?
Thirdly, it tends to come out tail heavy, so get rid of them hardwood dowls for pushrods. I know that you are thinking that if I put a big engine up front, that it will balance better, but Up goes the wing loading with that big engine. Use your battery pack to acheive balance, mine has been placed in front of the firewall.
It moves out smartly with that little .46, flies fast enough to look like a 1931 racer, and lands like a dreamboat !