thanks for the input and help...I'll use some 1/4 plate or angle iron internally and plug weld.

Ok so Im rather new to welding, but getting better with every mistake :) I plan on extending my camper rear frame 10" to hold a storage box The frame is 2x3x1/8 tube steel and the 10" insert sections are the same I was planning on a butt weld to keep it clean, but question the strength I c...