Found on Thing-iverse by GA_3D ! fantastic! Here are his recommendations:
This is a template for cutting 3-1/2 inch mortises for door hinges with 5/8-inch radius corners using a router with a 1/2-inch top-bearing bit. The photos should be pretty self-explanatory.
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I used PETG. 4 walls. 20% Honeycomb infill
I trusted the packaging on my hinges and did not measure them before printing, therefore I had to tweak the finished template to make it 90mm long instead of 3-1/2 inches. The SCAD file and the STL account for this; you can adjust scale factors in the SCAD if you like, or of course scale the STL in your slicing software. I would suggest pausing the print a few layers in and double-checking the dimensions against your actual hinge.
-- obviously will print in PETG for strength
0.2/0.4mm quality
4 walls 1.6/1.6mm
will print w/ support touching build plate and with face down to minimize them but also to have had strength
brim, paper and glue to make it perfect
infill 15% honeycomb will make it sturdy!!