Rotisseries rock!
About those welds.....
Can you see if there was enough heat to penetrate the thicker piece?
it looks to me to be quite thick on top but not much discoloring which is an indicator of proper penetration. hard to say with those pics but just in case....
I would cut up some scraps of that tubing, create a good clean, chamfered and tight joint and practice my welds and inspect them from the inside to see any penetration indicators. Adjust settings and repeat till you are happy with the results.
Apart from that, enjoy the rebuild! Mine has been sitting for 2 years on the rotisserie with nil progress...Sigh.....