Tell us about yourself!
If you used plywood ripped into strips instead of 2X4s for the strongbacks, you wouldn't have to worry about finding perfectly straight ones. I live in a humid climate, and have brought home wood I thought was straight, only to find it very warped a couple of weeks later. Or maybe it was those shots of tequila that I did to calm my nerves... :) My workbench is getting pretty crufty and dinged up, looks to be a good way to get it true again.
Something to remember- the contour gauge described here has to move at right angles to the project. If there is any undercut, the gauge can't see it. Also, as the curve starts to wrap around to the side, the contour gauge become less and less accurate. There are other methods, like using a compass to scribe a curve, or the tick/joggle stick method that seem to me to be more useful. I'm rebuilding the inside of an Airstream trailer, so copying curves is something that I'm doing way too much!
I went to Home Depot to get the propane BBQ parts, but the replacement burner has a slip fitting for the needle valve to fit into. Is there some sort of part to adapt from 3/8" flare to the slip fitting?