I made a 2 hole version for my 10" Dob years ago. Originally cut 1 x 90 mm hole but found it fouled the spider/2ndary.
I then added the 80 mm in the correct position clear of the tube sides & spider etc. This is the one I use as the aperture stop. Works extremely well with focusing, even being slightly diff. sizes. Just used 200 gsm card stock from the newsagents. Sprayed it with clear lacquer to waterproof.
HTH.
L.