Beta MTN-Goat 3.5

Added a new flushed out engine which goes great with a new direct propeller so no need for shifting (still an option with a DCT propeller.)

Aside from that I reworked a bunch of the jbeam and adjusted properties, the wheels should be stronger with turns. Now there is a psi slider that barely does a thing. On top of that I strengthened flaps and ailerons allowing for faster flight speeds and remaining in one piece.

Finally, added a tail counterweight, perfect for bigger engine swaps and centering the CG.

Little montage I made: