Wider IS better! Just wondering if you had a reason beyond the obvious.
Your thoughts on insetting your tube, maybe an 1/8", to make a full weld that you wouldn't have to grind along with your outer fillet weld? This way you would still have 3/8" tube contact on the 1/2" plate with weld on both sides.
Great work! It's always a pleasure to make tools that work better and will last longer than what you could find on a shelf!