Re do front diagonal longeron due to imperfect fitting with lower longeron. Square tubing 5/8" x 0.035 longeron fitting completed however one of the square tube also having imperfect fitting with lower longeron.Re cut another square tube, match it with the longeron and its fit nicely. Note: To make full use of mouse tail file. Tube jigger shall be used ONLY for 90 deg fitting. Manual tube cutting and filling for diagonal longeron. Jigger tube cutting may sometime result an imperfect cutting.