So tack them on under the car. Doesn't take many tacks.

ANY time you weld on a housing it can warp.

Look into old school welders straightening big wide-flange beams by welding here and there. You'll get religion.

Stitch the welds to spread heat around.

I'd suggest checking straightness with the jig and then bending to suit.

If you have the pucks for the bar, you are then one length of cold rolled steel away from your own setup.

RR I think you're going to want to experience this yourself.

R.