[sigo'suite]

Tom, You are correct because mine is a TK3 and the overall length of the slideout is 12'10"; windows are exactly 10' out to out of the trim.

The slide out toppers should be no problem if they are mounted like mine which is: at the very bottom of the top trim piece, as you say. No part of the awning, or the support arms comes any higher than the bottom of that trim piece.

Now it is just a matter of determining the proper awning length for your application, I would think. The drip rail is simply cut to proper length from stock lengths.

Glad to be of help.