My CG is about 9" measured upright w/wings on.(top wing) 18.4lbs DA50/stock muffler. My standoffs pushed the engine out so far that the cowl did not cover the bottom side entirely, I had to epoxy on a cut-out scrap piece of cowl on each side. The H-L screws & carb are completely outside of the firewall this way. I have not had any problems with firewall & vibration after 75-100 flights. I have had other parts coming loose from vibration: Cabane screws, wooden cabane mounting rails under the top sheeting, LG screws. Locktite every screw and beef up the cabane mounting. There is more info on the DV in the Giant Scale 3-D forum threads. This plane is the easiest I've ever had to harrier, you could do it with one hand in your pocket!