Maybe a bit long winded but it works for me
1 google SG headstock
2 find a picture that is straight on and sharp and copy to your pc
3 edit picture in 'paint' at 100% and depending on your screen size measure and resize the picture
4 remember the resize % as your pc will always be the same
5 print out and check measurements (I use the nut width as my guide)
6 if the print out is wrong just resize until it prints lifesize
7 cut out the picture and paste on your stock blank with a light water base glue