Thought I just share this experience today.
Bought a really mint condition carbon chassis TC, but then found 8 flat head screws which will not budge. A few were on the same side of the front and rear bulkhead and so the method of turning the bulkhead round to unscrew will not work, needed to at least remove until the one remaining screw is left.
Had previous experience before and I know if I were to put in more strength the hex heads will strip.
I do not wish to use a dremel for fear of damaging the carbon chassis. Last resort that I thought I'd use.
1) i used a lighter and heat up the screw head and aluminium bulkhead hoping to unbind the screw. after some tapping using a hammer on the driver on top of the screw head, a few came off.
2) left the chassis in the freezer overnight, one came off after a little bit more hammer work.
3) stick that part of the chassis in boiling water hoping that the expansion will unbind? a few more came off with some tapping again.
4) only 2 left which is on the same suspension mount. used an impact drill and drilled with the smallest drill bit I could find, anti clockwise. did not drill through the head but just left it on for 4-5 seconds, there was still a bit of head left for the hex driver to hang on to. somehow the impact of the drill turning anticlockwise managed to unbind the screw and it came out with no fuss.
Countersunk flat head screws love to bind to carbon chassis. Grease will help with the contact area between the screw and the chassis.
Excellant work done on my part if I may say so myself. The only cost was a few damaged screws.