I'm having a bit of a nightmare building a new Campy Record rear hub onto a DT Swiss R460 with 292mm and 290mm (drive side) spokes. It's my first rear wheel with cassette build.
The drive-side spokes have to be very tight to maintain the dish. As soon as the non-drive side spokes are tensioned much beyond the nipple driver stage, the dishing goes out again and the drive-sides need ratcheting up to a point where they can't go any further.
I got my spoke lengths from Edd, and Wheelpro gives about .2mm shorter. Maybe the ERD is out, even though internet seems to agree on 596mm?
Should I try longer spokes?