Im gonna have to stick with Les and Hal on this one... Monkeying around with that thermal cutout isn't something I'd do personally without an OEM part spec'd from the can mfr... It's much easier to knock the old can into the ceiling space and install a cut-in can in its place than to devote hours into seeking a part.
Just FYI, have you made sure your bulb wattage is at or below the can's specified max wattage?
Have you tried an edison base fluorescent lamp in place of an incandescent bulb? they typically generate a fraction of the heat
If you do replace the can, make sure you get an IC rated can if it's going to be surrounded by insulation.