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.
15 LibTech TRS HP . 15 NS Snowtrooper . 15 NS Ripsaw . 13 Salomon Pow Snake
15 Now Drive . 14 Now Drive
14 Flow Hylite