Back on my lotus eleven chassis fitting suspension pick ups and the like. Gas fusion welding i am having a problem now and again with the weld bubble exploding and making a mess of me weld.
Contamination had problems when doing the Six, & we had blasted the frame, do you have breather holes if you try to close tube it can blow at final closing.
Had a stair railing corner post I built out of 40 x 3mm box blow a tear 3 inches down one corner it went of like a 12 bore was in the sun most of the day though