Just to add, the maximum magnification allowed is 12x mag and if SFT shooters are in a group with non-SFT shooters, the SFTer's must shoot first in the lane. Everything else is the same as FT, windicators, butt hooks etc.
SFT was born in NEFTA being the brainchild of Matt Hirst and Dave Baines. It was adopted by the BFTA Grand Prix series for a few years, but has sadly been dropped from the Grand Prix series.
It's still very much alive and kicking in NEFTA though and has a strong following. Don't know if any other regions support SFT, so it may just be a NEFTA thing now.