ORIGINAL: buzzard bait
There are lots of terrific .36 engines out there that weigh around 11 - 12 ozs and have more power than almost any .40 of 20 years ago, like my Irvine .36 or the TT .36. They are excellent choices for lots of the lighter .40-size planes.
Jim
Silly us. We didn't realize that a .36 engine fell within the
REQUESTED .40 -.50 size. Nor did we realize we were comparing to 20 year old engines. Again, silly us.
While your point of them being fine for light .40 size planes is a valid one they also limit future use to smaller/lighter planes.