Measure, level, measure again, level again, measure again and again, level again and again, think about it, dream about it, CUT ONCE.
Then file again and again till it's feels right.
Note the original tripart bridge still in place, but acting as a guide for the new two leg bridge about to take its place.
The new bridge was welded in place just rotated shy of an inch with the old bridge so that the ring would not lose form. The welds on this need be dooky and well tempered.
Just think what the welders facial expressions looked like when I walked into the shop with this "Lost in Space meets the Munsters" gadget as you see it. More like a science project on LSD.