I can't complain, though, because it keeps the game more fair.
I agree. Also, if it works on this scale, why not just stick two fusion engines in a mech? It would be lighter to have two 200 engines than one 400. But I guess this could be explained away with "shielding," "interference," and various other pseudo explanations.
P.S. I think if super heavy mechs which could take two or more engine slots, but with a -1 or -2 modifier on incoming fire due to a massive increase in girth could be cool. Just saying.