I just cut this up in Fusion. I'll attempt a print now. Its The OG feedneck adapter, sliced, and lofted at a 45* angle for powerfeed guns.

Printed using the same settings as the OP. I'd recommend increasing infill to 40 or 50% as with a heavier hopper it seems like it'll want to roll over on the marker feedneck. With a non powered hopper it should be fine.