Created this holder to holster my Springfield Arms 1911A1, chambered in .45ACP. It's meant to mount under a desk, and hold the gun securely. Printed in PLA, at 25% infill with 3 walls. It fits snugly when inserted all the way (giggity) and hasn't scratched the finish on my pistol. Could be mounted vertically, however I haven't tested it. Best to print it in the orientation as is, that way you don't have to worry about supports.

I've been meaning to try and print this in TPU, so that it's a little softer on the finish.

NOTE: If you have upgraded rear sights, you may need to alter the file slightly; as the file is, there's just a little over 6-10MM of clearance between the standard rear sights and the surface the mount is attached to.

I used the 'Hacked profile' in Cura 5.0; you create a new profile using one of the Ultimaker profiles that closely resembles your machine (For me, it was the Ultimaker S3) and then change the printer parameters in the profile to reflect your machine settings (i.e., bed size, nozzle offset, z height, start/end GCode, etc). There's actually a great video by CHEP on YouTube, I'll link to it here: 
Faster 100% Infill Prints with Cura 4.13 on Ender 3D Printer.