Hope its not too late but I encountered this problem on a friend's car this evening.
He'd stripped the inside teeth of one of the Torx T50 screws so gave it over to me to try and sort it.
I thought there would be no way of getting it out, apart from using a welder (won't go into detail here), but before doing so tried this 3/8" speed brace and it came out fine.
Before using the brace I had tried putting the Tork bit on the end of an impact driver but even after several goes on it with a lump hammer it hadn't budged.
The brace worked perfectly on the ones without the mangled heads too.
not looking good
3/8" drive speed brace breaks the rust bond
I appreciate not everyone has one of these but it is something you would use again so perhaps worth investing in