Solortex is the best. For me Mk was always a pain to work with. 21st Century is good and the Tex. Haven`t covered anything in years, I mostly paint now but I still have a few iron on covered planes. A few years ago I did the rudder of my H9 T6 and used Tex to cover it back. It was as easy as ever with all the curves. Don`t know why people still use that MK stuff, its the worst. The 21st Century was far better, much stronger and easier to work with.