Dave that frame is looking awesome. Eventually you are going to have to come out west and find a rust free body to put on that thing. Why? Cause that frame is going to out last you me and most other guys on this board by a long time!!! If the body gets trashed or rusted out, its time for more tubework right?
Excellent Job man
Oh and my two cents on the welding grinding. I have boxed a couple frames on a couple different rigs. One was on an a square like ours but that was being hot rodded. We ground down every single weld on it but made sure to V everything. We were usually only grinding down the top 15% of the weld. Less if we were careful.
It sure looked nice when we were done. The powdercoater said he hadn't seen many frames come in that were that nice.
Unfortunately as with many things I do I forget to take pictures so no pics of it.
If you prep the weld properly (like your Vs) then grinding the weld is no problem.