Mike cz, that's really nice. If the 14mm MCPCB looks like it does in your photo, then you can trim it down to 11.5mm as you've shown. The problem I've seen with the
DX11023 XR-E Q5 on a 14mm board is that the oval-shaped LED+ and LED- solder pads are placed at an angle on the board. With the solder pads angled, they stick out farther than they need to. I think you would be hard-pressed to trim that version down below 13mm. Even if the DX11023 had the solder pads aligned north-south as shown on the DX web page and in Mike cz's photo, the DX11023's solder pads themselves look to be too large. The version that I bought that had the angled solder pads has skinnier, more oval pads.
So the trick seems to be to find a 14mm board that has skinny solder pads that are properly aligned. You need both to be able to trim the board down to 11.5mm.