nice work, and agree with wolfmarsh to add a hole just slightly undersize (press fit) or slightly oversize and people can add a dab of silicon to lock it on.

I have a few items on Shapeways now and tend to list both the original version and a upgraded version with some improvements - check out the ball launch arm - original and an upgraded version with increased webbing etc so hopefully people only ever buy one. I also keep the originals at original colour and upgraded as multiple colour option for modding options.

as for making public, there is a tab when you go into the edit details tab and click it then it opens it up and there will be another tab making it available for sale.

checked out your shapeways models wolfmarsh - nice work, maybe put pinball in the title so it can be found by others in a common search "pinball" so others can benefit from your work.

from my experience and checking measurements with shapeways items there is a 0.2mm variance over size (I think from memory) in regards to the tolerance.

Shapeways will print the design solid unless you have it hollowed out but you will then need certain material specific breather / cleanout holes. Likewise with wall thickness it averages out at least 1.2mm wall thickness like for the collar to go around the shaft.

could you possibly extend the front about 1-2mm and then allow a recess for the screw head and maintain the screw on type feature but then maintain the sleeve style (with a slightly larger hole to be a size slide on fit) strengthened with a radius so the target is stronger than original. The down side is the target face sits out 2mm more than standard but if it is a end shot feature it shouldn't matter. Then it is easily removed and you can insure a decal over the screw head so it is a clean look.

just to help those wanting to design and print at shapeways and want to factor in Shapeways printing tolerances, I have put up a few models in metric for posts and then for holes and I will also do imperial versions tomorrow.

Calibration tool holes
https://www.shapeways.com/model/1976152/shapeways-3d-print-calibration-tool-metric-hole.html?li=search-results&materialId=62

Calibration tool posts
https://www.shapeways.com/model/1976217/shapeways-3d-print-calibration-tool-metric-post.html?li=search-results&materialId=27