Powder coat for lower control arms

[71CHEVYSHORTBED402]

I'm having the lower control arms added with the next batch for powder coat (pictured). I've seen some seal off the surface for the coil spring. Why is that? I spoke to a guy who builds these trucks and he says it's unnecessary.

Also, should the hole where the ball joint inserts be taped off? Have you experienced a problem installing lower ball joints when the holes are powder coated? I'll ask they tape of the threads for the control arm shaft.

Other than that, I think everything else here is A-OK for powder coat. I'll ask they not powder the mounting surface of the pumpkin cover. Apparently you have to ask, because they coated the surface on the axle (yikes) and I had to strip it. Strikes me the spindles would be fine, so long as the threads and spindle itself are protected. I'm assuming the mounting surfaces are OK to coat. Thanks for any input.