Somehow, the video stops after about 6min 24s
Dunno if you had already planned that, but if your engine bolts went all the way from left to right, or if the engine effectively acted as a giant spacer between both sides, then you'd better also add a spacer between the left and right side to keep the frame rigid without pinching it together.
The original engine is load-bearing in these designs, so something solid needs to be there to replace its secondary function.