Can't hardly find squat on the APS-4 from the net. I have a three view drawing of it mounted to a P-38M - if you PM me your address I'll send it to you along with a couple close ups of the P-38M nose. This site indicates that it was about the size of a 500lb bomb.
http://www.duxfordradiosociety.org/restoration/equip/aps4/aps4.html
The APS -4 was carried on hard points of certain AC and should be the same or very similar to the one on the P-38M.
I was thinking of maybe choosing it in the AC weapon menu. If it is modeled as a pylon it would have to be AC specific I think(?) and that would cause some problems. But if it was made to be like a bomb or a drop tank wouldn't that be OK? Something that could mount to a hard point as a 'weapon'?
Thanks for taking a look