I have a BVM A-4 kit that I have not started yet. This is the same kit that Larry Wolfe sells at Jet Hanger Hobbies. It uses a Turbax 1 fan unit and K&B 7.5,.48 or OS. 46 ducted fan engine. These are 5" fans, Yellow aircraft calls for a .65 to .91 engine and Dynamax fan in the same size plane. I have heard that they both have about the same speed due to the extra weight of the bigger engine-more fuel onboard. The extra weight would also affect landing speed & handling. I also have a Regal Eagle I've been flying for the past two years, it's a great flying plane. If I can be of any help, let me know. I have been collecting info on the A-4 and could send you some pics.