Whether you make your rod pipe by drilling, ie making a tube, or by forming around a mandrel, when you attach it to your rib, you will be filing a flat on the pipe that pierces or almost pierces the cylinder. This flat corresponds to the flat you will have filed in your under-rib, so that the hole in your pipe is continuous with the concave groove of the rib. Just soldering a pipe onto the rib without this filing will result in a poor set up with a gap between your rod and the rib. To my eye, this is poor workmanship.