Chris,

I cant figure how you are 1/4" short.

I didn't have a problem fitting my OS 46 LA, so maybee you have to get longer engine mounts.

I don'y know how critical the measurements are.

Anyway Chris, I cant see any problems with your suggestion of adding another 1/4" ply to the firewall.

Good luck witk it Chris, the LT 40 flies great. You will love this very forgiving trainer.

I have changed my engine now to a 49 MVVS. Man, does she honk.

Sidekick.