Then you'd have to worry about the outer axle hitting the bottom of the coupler box.
I'd rather see the tooling modified so that coupler boxes are properly integrated. Then model could stand at the proper height without compromising end detail, or the axle hitting the coupler box, or having to use "underslung" couplers.
Emphasis on the word "properly."
Athearn may have taken a few steps backward when they modified the PS 2600 from truck-mounted couplers to coupler boxes that appear to be integrated into the frame.
http://www.athearn.com/Products/Default.aspx?ProdID=ATH16320The ride height on the older runs is an eyesore, but it is relatively easy to fix with BLMA trucks and 903/905 couplers (or any other coupler boxes that don't hit the axles)
It wasn't unreasonable to assume that they'd fix the ride height when they added the new coupler boxes...but they didn't...
I haven't bought any of them to say for sure, but unless the new coupler boxes are not integrated or are at least easy to remove without damaging the body, it's not unreasonable to assume that lowering these would be a total PITA.