You need a counter rail ( baton around 60x20mm) to rear of top edge to fit capping rail too.
The closer the top and bottom rails are to end of feather edge the less they can warp or twist .
I would question your inclination , you are creating a potential problem while doing nothing would seem the best option.
Steel roof supports will last years even with rust .
Have a few £k in stocks and share ISA , only been investing 3 months and currently just over 7% up ( cash value just over £600). So way better than a cash isa . ( everything bounced back after some reduction due to the War)