You need to deal directly with the builder himself. And his biggest concern should be that the bike fits you properly and rides the way you want it to. Geometry plays a HUGE role in this and he should be asking you all kinds of questions regarding your riding habits, terrain, how you want the bike to steer, take bumps, etc. If that aint happening, IMO look for another builder.

Something a good builder (with a conscious) would ask immediately is why do you want a "keirin-style frame for road/commuting use." Your answer may satisfy him and he might build it for you, but it's something that would strike him as odd and worth discussing before proceeding.

Not Scrod. Apologies.