It appears that's going to be the key to getting these bolts out.
My plan is to soak the bolts with a high grade penetrating oil overnight, then gently warm the aluminum rods they're screwed into while applying cold to the bolts themselves, just before I try to turn them out.
Along the way I'll try the tapping trick to try and break the corrosion bonds.
I'll get some pics up in a follow-up post, so folks can see the project. I'll scan back through here and ping everyone who offered their advice.
Much appreciated!
Ping me too when it’s solved. I’ve been lurking but am interested. Thanks