Weld The Spacers
Lay the frame on it’s side.
Protect the cylinder and press feet so that when you weld, spatter won’t stick. You could use some piece of metal or a nonflammable cloth.
On the inside, bottom edge, weld the interior of the spacer inwards as far as you can. This should be an inch or more. Do this in all 4 corners accessable from this side of the frame. See the photo.
Weld the top 100%, and grind it flush.
Flip over the frame.
Weld this side as you did the other side, also welding inside the spacers.