To change dimensions, please download the F3D file and change parameters.
The uploaded one has a hole of 16x26mm
For pinning to the skadis board please use the mini t-clip version here ! (The original ones won't work because it sticks too much on the sides)
Because it uses only one clip, I suggest downloading the version for the unpainted skadis if you have a painted skadis, for tighter fit!
If you have unpainted skadis, you would need to make yourself a narrower version by adjusting parameters of the t-clip.