So then get the RK30. It's the TT30 with a urethane back. If Flux is able to sell you a pair of DS45 urethane backs, I'm almost positive they'll slip right into the Feedback base.
16 NS West . 15 NS Snowtrooper Brother in Arms Edition . 13 Salomon Pow Snake
16 Rome Katana . 15 Now Drive . 14 Burton Genesis
14 Flow Hylite