One fix for the cargo deck being above the ground could be the installation, or at least mention of an integral crane/hoist that swings out when the door is opened. You could even have it run horizontally across the entire section (with a airtight seal between air raft and cargo bay) so that you could, if necessary winch up the air raft or store additional cargo in the air raft bay. on each side of the ship it would extend, of, at least slightly more width than an air raft. If it's on rails it could easily be extruded as needed. Materials of that TL would be more than strong enough to support 4dtons.
Alternatively you could make it so their is ramp that extrudes, or is flush with the outer hull and swings out and down. The angle would be kinda steep, but would make a/g loading easier. A small winch could easily pull up loads on a a/g skid. Or even put in a small a/g loader that is stowed in the cargo bay, much like a pallet jack is today on trucks. takes up almost no space and is quite useful. It's not like you'll be hauling a lot of big cargo in that cramped space anyways.
What's the purpose the tie-fighter wings though? The stubby wings would probably do ok. Heck, you could hang some engines off of them and free up some deck space and still be true to the contest.
