Question about weld grinding for best appearance

[digitalwelder]

Hello,
I am building a bumper for my truck and butt welding the joints. when i grind a V joint top and bottom and weld on top and bottom, i get a valley on top of the 2 pieces. When i try to grind the top surface for cosmetic purposes. I end up grinding the surrounding metal because the weld ends up being lower in the valley.
When i grind a V only on the bottom and weld from the bottom, i get penetration through the top but when i grind that small protrusion flat, I find that there is still a bit of a valley and i end up grinding more of a valley to get a smooth appearance.
I have attached hand drawings.
My question is what is the best butt weld/grinding technique to use to get a nice flat appearance on the outside weld.
Using Miller 180 autoset.

Thanks in advance for your help.