Hmm. If somebody managed to squeeze a straight six in, there must have been bulkhead mods I suspect......

I agree with Mr Tony that it's an odd choice. Well balanced, but long, so not compact. It will put the weight forward in the chassis - unlike the V6 which has a foot of space between the engine and crosshead. In a given length a longer engine equals less cabin space, so the compromise must be the +2 bit.
But then I'm a Trad man so have nothing more than interested curiousity...........