One think my dad always said work at the right height. He was meaning use a table or bench to put what your working on and not bend down. The motor bike I will have to do some welding on for the new foot pegs I have.
It is necessary to remove the gas tank, carb (engine also), and wheels to not burn them during the welding. So anyway then it is light (not super light) enough so though that I can put it up on a work bench to work on it.
I though am guilty of not using the bench enough, since not everything requires removal of enough components that I can lift it. Currently at 130 lbs and probably will be adding 7 more with the brackets.
A way I found I could make the angles for welding metal parts stay in position, I just took some thin flexible steel sheet and welded it to the two thicker metal parts to be joined.
Then I went back to my bike and kept bending the joint made of the flexible metal till it was true with level and t-square. Simply carry it over to a vise clamped to a bench top and weld it just a bit.
Go back and check. If not correct, then break small weld and bend flexible metal for another attempt. Then when right fully weld up and grind away the thin metal and who know to the wiser that it was even ever there in the first place.