The horizontal tube 1/2 x 0.035 (upper and lower) at the tail end is completed - sta 154 3/8. The cross diagonal 1/2 x 0.035 is than trim at both end and it fits nicely - between sta 115 3/8 ~ 154 3/8. A cross diagonal between the upper and lower (box area) is than done - sta 115 3/8. There was a bit of spacing (probably 1/16") and after checking it can be welded.
