I can almost always find a way to move the batt around. If the model has openings in the bottom(through the lite ply, for example) I just seal the covering around the edges of said opening, remove the covering over the open part, put a lip around the inside edge of the opening, and make a cover out of material the same thickness as the fuse material. Actual location of hatch depends on where the batt sits on outside of fuse to get plane to balance. Can either cover hatch and screw in place or cover hatch directly to fuse. If there are no openings already, I make one.