Two things.

I had to clear some of the plywood under the engine to give room for the aluminum spar to go through and with the added weight of the new mount and the heavier engine I'm not that far from the CG, I had it at around 114 mm last time ( wrote it on the canopy frame ) The CG right now without the fuel tank, which seats forward of the CG and without the batts is at 83 mm from the front of the spar.

All this means, that it will not need the 1 1/2 lbs of lead on the rear of the fuse to get a good CG point and that it will come to a good CG point by locating the batts at the right location.