On an 8' older valley bar box that I just put velocity pro onto I thought I had it leveled. In fact I can slow roll a ball from any corner to any corner without ANY roll out. It rolls true end to end side to side, but if you put 3-4 balls frozen on the rail and slow roll the lead ball down the rail it will roll away from the pocket from a diamond out. On every corner. It also slow rolls away on the short rail. I'm pretty sure it's a build up of glue cause I scraped alot off of the underside of the pockets to get a smooth surface to fold the new cloth to. By alot I mean at least 3 recover jobs. Where I think I screwed up is I didn't clean up the area where the slate sits. I cut the velocity flush as recommended but the old glue and stuff is still there. Funny, I think I just answered my own question but if there is something I'm not aware of I'm asking. Don