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.
17 Korua Apollo . 17 Nitro Treehugger . 17 Lib x Lost Mayhem Short Fat . 17 Jones Storm Chaser . 17 Ride Warpig . 16 Never Summer Swift
17 Burton Malavita Wing . 16 Burton Genesis X
16 Flow Talon