[RWebb]

The low center-of-gravity of the flat-6 engine configuration, is not a huge improvement over a V-type engine design - the really heavy stuff (the crank, the int. shaft, the oil pump) is still low in the frame.

The heads and valve train are higher, and the induction system may be higher. These items weigh a lot less tho.

The advantages of the V-type are a much stronger block (case); ease of manf. and repair, and sealing (since you don't need to split it to do work or put it together).

The imbalances in a V-8 create an interesting harmonic structure ("rumble") and are fairly well controlled, altho the imbalances are greater than in a flat design.

(A V-6 is a horribly imbalanced design and I hate hate hate them -- the V-6 does go well with cup-holders however.)

If you REALLY want a low CG, then you need to use a distributed power system, such as GM showcased in their flat platform fuel cell electric vehicle concept. The entire powertrain is in a few inches of thickness that forms the chassis. You don't get that mechanical noise from an IC engine of course, but you would get tons of very clean torque, and a low CG. There are pics of the concept on the Internet somewhere...