I am getting ready to convert to a Wynn Enviormental filter and a Thien Internal Baffle on my Delta 50-850 DC. From what I have read, the opening to the filter area is too large (11.5"). Question - can I just make a hardboard donut that reduces the opening to 8" or do I need to add a pipe to go down into the area between the inlet and the baffle (hope I am explaining this correctly) ?