This model needs to be used with dowels. The holes of the mount are having around 20-28 mm and should fit (wooden) dowels (like in my case). If there are any troubles i've uploaded the cad model for adjustments. 

If there are a lot of wished for a certain measurement i can adapt it aswell :)

I recommend it printing with some more infill and maybe thougher materials. Maybe you have to check on your own. In any case just use more of the mounts inbetween of a dowel. 

My print settings:

Material: Polymaker ABS

Layer height: 0.2mm

Infill ratio: 40%

Wall loops: 4

If it's very close and the dowels are barely not fitting - just use a little sanding paper and sand down the holes.

2.5kg Spools Version available here.