Well, on the Lightning, the plenum going from the TB to the blower is basically the same size as most of the single blade TBs on the market. You could make a larger TB, but it really wouldn't do much good unless you've extrude honed your plenum, or you have one of the Works blowers, which have a new intake casting and can support a larger TB.
As for entry design, rear and side are actually the same thing. The Cobra uses a side entry blower, but it's really a rear entry, because the "side" entrance is just an extension off the rear of the case. It still ingests air at the rear of the rotors. The Lightning on the other hand, is actually a "top" inlet. The intake from the TB goes into the top of the case, not the rear. This is a poor design, but it packages well. The reason it's poor is because as the air enters the blower, it hits the top rear corner of the rotors, and the air gets "paddled" as it enters. Also, the top inlet takes away from the surface area that the rotors contact the case, which reduces displacement. So even though the Lightning has 112 ci rotor packs, the blower is really only about 95 ci.