Wow. You have my sympathies. I've built a lot of resin kits, and I've never seen it warp that bad. Is this a recast, by any chance?
Here's what I would do:
A) Straighten the supports by heating them in hot water, or w/ a hair dryer.
B) Carefully, carefully drill a hole in either the hull or the engine nacelles (depending on which will cause the least irrepairable damage) all the way through, and into the engine support. Use a pin vice and go sloooow so that you drill straight down the center of the support, all the way to the other side.
C) Run a length of brass or steel rod through the hole. Make sure it's long enough to support the boom, but not so long that it interferes w/ the rod you need to put in the other side. You can then fill, sand and repaint over the drill sites.
You may also want to drill a hole into the engine nacelle forward of the boom (on the top or bottom maybe), and but some small lead fishing weights ito it, to balance the nacelle both forward and aft of the boom. Fill and sand just like the other holes.
Good luck - JC