Mikey,
There is a detailed description of how to make filters from thin film material on my website.
http://joe-cali.com/eclipses/EQUIPME...arfilters.html
I am in the process of updating the first part of the article talking about filter materials but the section on construction of the filter holders won't change.
I have used the same method to make a full aperture 8" filter for my Vixen VC200L. However I make the flange double thickness foam core.
Cheers
Joe