Ah, got ya now, sorry if it was in one of the earlier posts but i don`t read everything and if so, my bad.
since you mentioned that it is expendable then I think you should do some work on the nacelle joining area. because when in extended mode the nacelle are doesn't fit, sorry if I aren't making much sense but I`ll try to show you what I mean.
-The areas where the nacelles joins the read line shouldn't be happening it should follow the red line and not come into contact with the extension bit(cant remember the name), that's what it should follow in my opinion.