after mucking around with belt tension trying to get rid of what I thought was belt skip I have just realised it was the stinkin' 48p spur I was running . I didnt have a 32p pinion when I built so I just put the 48p on with my castle 1410 sct combo. After doing some heavy braking moves at my feet on concrete I finally worked out the skipping noise was coming from the rear slipper area not the front clicker / pulley area . after checking mesh for the tenth time I noticed the spur teeth have just feathered slightly, enough to hold the pinion to what felt like a good mesh . moral of the story , ditch your 48p setup if you are using a castle 1410 sct combo and go 32p . I am using 15-62 , same as 23-93 , 10.6 FDR.