Here's Strike Recon Union (SRU) showing the way in rapid prototyping using a 3D Printer. The prototype shown here is there improvement on the XDM pistol, showing you the slide coming with a floating rail system. You can use this rail to mount optics and be able to shoot without the optics moving with the slide so it won't ruin your aiming. Furthermore, no need for modifications on your XDM to install a mounting unit.