Printed really well without supports in the supplied orientation, kudos for that! I printed this on my Prusa MK4 in Hatchbox PETG with a 0.4 nozzle using Prusaslicer's 0.20 STRUCTURAL settings.
The hole for an M3 heat insert could've been a bit deeper to accommodate the ones I had, but that might be more on me. I used an 20mm M3 bolt instead of the recommended 30mm, and it _actually_ could have been slightly shorter. After snipping off ~1/4 or 1/5th of the length, an idler spring from one of my older MK3s was the perfect length for this.
The only magnets I had lying around that'd fit were 8x3mm, if I had to do it over again, I _might_ try using 8x4 or 8x8mm ones and print an 8x1mm piece of plastic to go over the top of the holes. Regardless, with 3x of those magnets in each hole, it holds _very_ securely!
Edit: I printed a second one and only inserted 2 of the 8x3 magnets in each hole and it has _noticeably_ less holding power, such that I'm going to go back and glue in a third at some point. (edited)
