I do plan on skimming the rail surfaces but not all to getter. My plan is to fome the C section weld in the gussets then machine each rail separately, then weld the whole thing together. I have a 2" thick surface ground welding table I can clamp it to while welding. I'm hoping this will keep it straight enough. I did not think about the pads which I like so I added 3/16 pads under the rails for machining. Thank you :)