I would not expect the level of customer support that you would get from BUSA but I've seen people reporting on a few builds of Valueplanes stuff. It seems like it will probably build in to a flyable airplane. A downloaded copy of the manual is probably the best you are going to get. Regarding the engine. A 25-26 cc engine will work okay for lighter planes like the Sopwiths and Nieuports but the larger and heavier Fokker DVII, Spad 13 and the SE5a tend to do better with G-38s and larger. If you go with a gas engine i would suggest paying a lot of attention to tying the firewall to the rest of the fuselage structure.