[widebody911]

There's no real sin in the weld bead coming out the other side, and if you're A-R you can always grind on that side, too.

Doesn't look like you have much of a weld gap; without one, you'll warp the metal easier.

You should also clean off the undercoating near your weld; otherwise when it burns it will contaminate it.

I use a roloc #30 or #40 sanding wheel on a small 90° angle grinder - much less aggressive and more controllable than the angle grinder. For final cleanup I use a #50