The radial engine evolved by putting more cylinders on to smooth out the power stroke, and putting more banks or rows or cylinders to increase the power and capacity, eventually having to use liquid cooling rather than air cooling due to the difficulty in cooling the rear banks of cylinders.

Hence the early and inefficient 2 cylinder “V” radial evolved to being a 2 cyl, 6 row engine with liquid cooling, as the ultimate development of the radial engine:diablo:

smiles

Mark Pilkington

Mark, you seem to be describing an inline engine, the main clue being that a ‘radial’ works best with an odd number of cylinders.
Ray