Not sure this will help, but looking at your pictures, I'd worry about the metal nut on the badge side, or maybe your just installing the grommet. There is quite a bit of torque required to set that grommet and it could scar. I had good luck with a "breather hole tool" from precision drum company. Pretty cheap too.

I think the rollover from what i see in your picture is fine though. my two cents. Good luck.

Yes, use a hack saw and cut back some of the grommet, then use the tool you have. It works awesome, and you should end up with an original looking rolled over inside edge. too much grommet will crush like a can. Sorry I don't have an exact amount, but estimate for the rollover, and it will work, I put a dowel into the grommet to hold it while I cut, then I file the edge. I also get my best results when I start the grommet spreading with a tool like the one from precision, and then switch to the one you have to finish, but I am a bit of a perfectionist.

Dremel tool with a cutting wheel is nice for trimming those down... dowel in the grommet is an excellent idea if you don't have one.... in fact if I had thought of that... I might not have a dremel with a cutting wheel. DOH

That's way too much grommet inside the shell. Should be less than half that. When you cut it, get the cut as flat as possible so that it looks right after it's flared.

I strongly recommend the use of a nylon washer under the tool to protect the face of the grommet and the badge from being crushed/scratched. The little tool from precision drum is set up that way and is worth the money.

So 2 or 3/32" is all you need poking through to the inside to get a nice roll over? This thread is very helpful to me as well. I will be installing at least 3 maybe 4 Gretsch badges in the near future. I did buy the tool from Precision Drum and I do think a protection washer (nylon) is a good idea = makes sense.

Good luck with it. Would like to see the outcome

I would say around 1/8" (4/32) to make a nice flange on the inside. That first photo shows more than 1/4" coming thru...

If he uses the tool shown, there should be a little more than 1/8th. That tool will roll over the inner flange like an original grommet. It works great, and looks very professional when done correctly. I have used a few different tools to get the job done, and now I don't think I will do it any other way. As I stated above though, I still like to start a flange with a tool like precision sells, then switch to the tool shown to roll over the flange.