Had to get another center section for the whole saw i purchased to cut out the inspection panel for the pitot tube, Unfortunately the original one i bought looked like it was mislabeled as being compatible with a 4" hole saw and it was not.
Original was 3/8th but this only fits up to 1 1/4 sized hole saws, even though it was labeled up to 6", The 1/2" one is the one that fits the larger hole saws.