One last little tid bit here Dave. If you don't get that sheet metal top to fit just right, your site glasses will not fit thru the holes in the top sheet metal and the big nuts will not screw back on the site glasses. My opinion on your situation would be to get some arches that fit correctly. You certainly don't want to ruin the top by enlarging the holes for the site glasses. I am sure you can get some descent ones from someone on here? Kent.