I have the Momo Trek. it's a "D" cut wheel which i needed because i couldn't get my legs in the right position to "heel & toe". It really freed up some more room and is alot easier. Also heel and toe shifting is more of a big toe/little toe shift in the miata if your feet are bigger than a 7 (my opinion only). good luck with the search on the wheels.
Don't get a smaller wheel.. bend your gas pedal over slightly so that you're right leg is straighter when you're hell/toe'ing!!
Instead of turning my foot horizontal I have my pedals close so I can "roll" my foot more-so and it's just a million times more comfortable.
It bends easy so just try it and see what you like.