So been testing Horizon Shift on a load of PC and have noticed that it performs very differently on different systems.
My work PC will only run it well at 720p, my main PC likes to have Vsync off, my laptop likes 720p, Vsync on and needs threaded compositing enable (it's a slow laptop)
So to get around this I decided to make a little launcher in VB2013, which allows native res switching and some launch options. I can now get Horizon Shift to run pretty much perfectly on all the PC's I've tested it on, which is a relief.