As a left eye dominant, left handed firer in the RAF, I've been through all the various training routines and even had an eye patch issued for a while until it was decided to quote " get that fcuking pirate off my gate" unquote. The SUSAT allows the left eye dominant firer to shoot right handed with an improved sight picture - I have both eyes open, but aim for the bigger target!!
Apparently there is talk of a blanking arrangement in development/production, simply clips on and covers the left eye allowing the user to shoot with iron sight.
Its not advisable to try and shoot lefthanded - cocking handle to the nose has got to hurt!! Apparently there is a lefthanded version on the weapon, MOD are just too tight to buy them.