[clay68c10]

At this point, I like to start grinding the welds down and look for pin holes.
I'm a fair welder, but very realistic about how this goes. The gap isn't always perfect, the metal isn't always spotless, my welder is a decent one but not some hi-zoot machine. And my technique/work angle/eyesight isn't perfect every single tac either.
That said, get the brightest light you have and start shining it thru from the rear. I usually find a couple of pin-points to fix.
When I do this, I make sure to trim the "ball" off the end of the welding wire EVERY time I tac. This is the time to get those pin holes filled, and that pointy wire will get the heat in there better.
Definitely use a sharpie to mark them, you can't see em without the light, so I can't find them again unless I mark them. Then grind and repeat. Maybe you missed one and now is the time to get it done.