Hey Hopkins
I have always enjoyed reading your posts and here is a chance for me to give a little back.
This should have you covered. These are transparent and ready to go at 300 dpi. Can go higher if you need to, but these should do the trick. I find that most folks like decals in the 2" to 3.5" range end to end for the most part. So I started just under 1.5" and took you up to over 4" in 10% increments. One of these should be pretty close. They are exact size you can drag off the sheet and print it out and you can find the right size by holding them up to a headstock. If I am in-between and not quite there, let me know the exact size you need when you get home and it takes like 30 seconds to do it for you.
Cheers!
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One of those should be perfect. I have 3 different head stocks, A full size 4 inline, tele size, and a 2+2, same with guitars. I am sure there is a size in there for all of them.