The vacuum connection pipe has an external diameter of 31 mm. The diameter of the holes for the penetration of the drill tool is 15 mm, but can be increased as needed. The adapter is very effective in suction.
A support for support is required when printing. For the holes of 15 mm there is no need for support, their accuracy being not important. The walls have a thickness of 1.5 mm and are sufficiently rigid.
In the pictures are visible and some of the printing parameters used by me.

I have attached the file in FreeCad to be able to adapt the dimensions for your needs.
 

Success! ... I hope it is as useful as it was for me.