The very reason that the "triple square" is utilized is to effect significantly higher torque levels. The head can take all the force utilized to install the fastener to the specified torque. There are 12 load surfaces to take the force..........far better than any hex could ever do.

If you're stripping the triple square, I would check to see if you had the correct size and the fit is proper. Also check to ensure that the bit is going all the way to the bottom of the available space.

Finally, are you positive they are triple square screws and not Torx? Such errors have been made before.............

If all of the above has been verified...........carefully heat the fastener with a propane torch. If you just heat by the head...........be patient because the heat must travel down the fastener and heat the entire length. You wish the fastener to lengthen slightly to unload the head. I'd wait a good five minutes or so with the torch. A huge flame is not necessary or desired.

Once heated properly, the fastener is easily removed (provided you haven't totally stripped the head).