first i started with getting the keg top cut out. since i had an 8" flange, i had the hole in the keg cut appropriately. i then had the flange welded on to the keg top. (I'm neither a cutter nor a welder so i had to out source these procedures)
what we're looking for here is a smooth, sanitary weld.
i cut the lexan circle to fit the top of the flange lip. the lid was then drilled, and tapped to fit my compression fillings.
the gasket material i fashioned from a piece of latex tubing. i rolled the tubing back on itself, and snapped it over the other end.