Anyone on here use a sigma 7f standard that's willing to give a quick review? I'm very tempted but only ever used Rubi twin twin cutters. Also used a montolit quick a few times but annoying that you can see the pencil marks. I'm assuming this is the same for sigma? I do wonder though why a new sigma 7f is so cheap and the Rubi TS 30/40 equivalent is well over double the price?!!!