The Star reg mount has'nt just got a bulge on the side it is completely different on one side and the thread is milled into it i would not recommend just drilling and tapping a thread into your old frm there is just not enough material there to make it safe and they are only about £30 new from Planet is it worth all the trouble of buying a tap and a gauge and then possibly ballsing it up? Plus if you dont like the look of it your stuck with it whereas if you buy one and dont like it at least you can sell it and get some money back.