Horribly Twisted parts? I have a plan.

[SleeperService]

Well it's not mine actually it was shown to people at a model ship show years ago to align hull sections thus;

Get some short lengths of threaded rod as small as required I use 6" lengths of a BA thread I got from SleeperDad's clock repair suppliers with nuts and washers.

Align and tape the offending the offending parts together at both ends

Then, at one end only, add internal stiffening to correct twisting or depressions in the surface (if needed) attached only to the best side.

Drill through at 90 degrees to the centre-line with just enough clearance for the rod to pass through. Add a few washers and then a nut each end and tighten down until the best profile is achieved. 

Remove the tape and don't worry if the edges no longer meet unless it's consistent in which case you've over tightened and crushed the profile. DO NOT glue.

Repeat at the other end. Then check that the ends aren't twisted, if they are the threaded bars can be used to jig it straight by holes drilled into a thick piece of aluminium or similar.

Do the same for the centre bit. You'll need to separate the assembly a few times so I measure the exposed end of each stud above the nut of each rod. I use a piece of tape wrapped round the bar with the length of the OTHER end's length and whether it's top/bottom or port/starboard so it makes re-assembly a doddle.

When you're finally happy that everything is aligned and wing spars, bulkheads, and other internal bits are glued only to one half (it could be either or both) leave it to harden and cure for a couple of days.

Then split the assembly for the last time, apply glue to the mating faces of all parts that touch and put it back together quickly using the rods and jig. Check the alignment. Then double check. Then use an aggressive liquid glue all around and set aside in the jig for a week or so.

Take the finished part out and it should be straight and true as any kit. Fill all the tiny holes with the tapers from stretched sprue preferably from the same kit and you're done.

Until you know your stuff glue off-cuts of sprue from THIS kit until you find one that gives a solid join without dissolving the plastic.

 

I brought a Monogram 1/48 B-29 that had been in the sun in a shop window for far too long for 5 GBP. The fuselage halves had a 10 deg twist and were half an inch out of alignment. The wings were worse. My nephew has still got the resulting model. Correcting it as above took about four day's work over a month. Once you get the hang of it it's very relaxing remedial work. often the hardest part is finding a glue that's aggressive but doesn't dissolve everything.