Just laid down the bottom rails, clamped them in place ready for tacking up tomorrow, I am a bit worried about the joints on A1 to D1, once B2 has been tacked in place there is no way you are going to get a decent weld to join A1 and D1 because is will be hidden by B2! Same thing applies to the H uprights. Do you properly weld these obscured joints then tack on the other rails?

I tacked underneath and then fully welded m8, felt the same as u... have had no problems by doing that.

I welded them fully after I tacked them, then I ground all the welds flat.I also noticed a slight bow in the base which I straightened by putting one end on a piece of 3x2 and standing on the crossmembers . It's not an exact science, but it works.

yours, Pete

I tacked the entire bottom rail layout and then went after those joints that would be covered later on (by H for instance).

Where A,D, and B2 meet I found that I could increase the amps and penetrate the end of the A tube through the crook of D/B2.... fully welding the three pieces at the same time.

The heat of a full weld on top of a joint will cause the layout to curve upward. Flip it over regularly and fully weld the opposing joint to whip it back into shape. Pretty amazing how much it will move just from the heat (even with tack welding)... it took some practice, but I learned to strategically apply the welds and end up with something resembling straight.

-jim