I created this handle model so I could install handles in my surfboards. Included are STLs for installation jigs and bases for a Makita RT0701C Router ( for 1/4" and 3/8" straight bits). There are alternate files to compensate for slight variances in router bit sizes or printing tolerances. Also added a DeWalt base plate for 3/8" bit. Test them all in scrap foam to see what works best for you.
If you don't have that router you can use a Dremel or other rotary tool and eye ball it if you are just doing one installation.
I have printed in both ASA and PETG, ASA can have warping issues on the base but I've had good success. PETG is my preferred filament and epoxy resin or polyester resin sticks to both filaments very well. PLA is probably ok but I wanted maximum durability so ASA or PETG is the way to go. Clean with acetone and lnstall with resin and a mix of glass microbeads or cabosil, then fiberglass over the top of the handle, and cut open the openings once resin is set.
100% infill with supports on.
Not exact instructions on how to use the jigs but you get the idea from my website https://www.geckosurfboards.com/surfboard-building-router-jigs/
The author marked this model as their own original creation.