Routing exhaust through cross members?

[53Vipette]

I am finally getting back to working on my Monte again. I have rebuilt the perimeter frame out of 2x4x0.125 wall tubing. I have a cross member at about the middle of the frame for my truck arms. Then I have braces going forward basically from the truck arm mounts to the front torque boxes on the frame (see attached pics). I am thinking I want to some how route the exhaust through these by welding in some round tubing. I am just a little unsure on what size/ thickness to use. I am figuring on running oval exhaust, but is still think I am going to want the extra clearance. So if it goes through the braces, it will give me plenty of room. The exhaust is going to have to exit in front of the rear wheels, because it would be impossible to get it over the axle with the truck arms, panhard bar, and gas tank setup.

Thanks for any and all suggestions. I was thinking about using something like 4"x0.250 wall? Not sure what I need to maintain adequate strength?

You could always have the pass-throughs CNC Plasma or Water Jet cut and lap them over the existing tubing. I ran into the same issue on my trans cross member and ended up notching it to allow the exhaust space. To compensate for the notches I added some additional material to the top, if that makes sense.