You are also going to need to lengthen the LAAT by a few inches to make up for the size of the ATTE. I'm not sure mags will be the solution for holding it in place. The ATTE is extremely heavy and you'd end up adding a LOT of weight to the entire vehicle with mags large enough to hold it. I would recommend an under belly harness in addition to the side clamps that could fit over the middle legs.
I'm also not sure if ATOC has any reference shots of any use of this in it.. You may have a better chance catching the opening season 2 episode of Clone Wars. They land a bunch of ATTE's via LAAT in that one. You can watch the videos on cartoon network or maybe catch a repeat in HD on cartoon network..
I personal would love to tackle this, but I don't have an extra gunship to cut up
I'll be following this with great interest!