Well, here is a couple of 'mods' that I did to my 425. I made a frame stiffener for my 425 and 550 to reduce flex on the plastic frames. It is just a piece of aluminum that I attached to the motor mount, and then to the frame. I cut a piece of the front battery mount of off the 425 and then attached the 'filler' supplied in the kit for the lower mount, to the front to hold a 6s battery nicely. The filler is made in 3 pieces but I just snapped them together without glue so that it will come apart in case the frame halves need to be separated. Then glued and screwed the side pieces to the frame sides.