Mantis X is an amazing tool, but needs proper baseplate mods. the universal picattiny rail from Mantis and stick on back plate is something I gave up attempting to do.

Source Link on Thingiverse for you to modify, remix or whatever https://www.tinkercad.com/things/ihxWIFmZSDQ-mantis-x10-picattiny-adapters

Mantis X-10: https://mantisx.com/products/mantis-x10-elite

Mantis X10 adapters for Various Handguns:

• Walther PDP F series 18 round mags for https://waltherarms.com/shop/magazines/pdp-full-size-18-round-magazine
• XR920P magazine - this is practically Magpul PMAG GL19 mags https://magpul.com/pmag-15-gl9-glock-g19.html?mp_global_color=118
• CR920X Magazine - This is Shadow Systems CR920XP https://shadowsystemscorp.com/product/cr920x-magazine/

I printed these on my Lulzbot Mini2 with T-Glase from Taulman (I had the printer and an old roll of Taulman around).. but I think any PETG should work fine.