Felt Mats or ???

My table is the maplenoll ariadne which has a lead platter that is countersunk in the middle to account for the label thickness. Hence no pad is recommended as the clamp attempts to ensure solid contact of the lp to the platter. My platter does not have a vacuum system or outer ring clamp so severely warped records are not firmly contacted, but most other records are contacted by the entire platter. i did try a felt mat once but did not like the sound. it seemed the bass response was less