Here's a trick that works. Bolt up the brkt. that mounts to the frame. Then fill the tapered hole with body filler to make a plug. I greased the brkt. before I put the filler in. Once it was hard I popped out the plug I made from the filler and put it in a drill press and drilled a 3/8" hole through the centre of the plug. now I made a steel centre punch from 3/8" rod and put the plug back into the frame brkt. Which I put the steel centre punch through the plug and hammered the centre punch against the splash apron and marked the spot. Now it's spot on and you can open the hole up to the right size. remember to keep your hole saw square to face of the apron or frame. I go small first and then open the hole up as I need it. From the plug a friend made me a steel one so now the club has a tool to do this job. It works well and no guessing. John Poole