x.21 cables

anyone have any experience with making up x.21 cables? i'm on a project at the minute where we are in need of more length on some 3 metre x.21 cables and the pm seems to think it would save money if the engineers make up the cables on the fly. i've been told they're an absolute nightmare to make - anyone have any experience of this?

I've never made any but I have the wiring information somewhere if you need it

sorry Bishop only just got chance to respond - i've found some wiring info on the net but it looks like we're not going to have to make them up after all. i've been told by someone in the office that they're a nightmare to crimp and it would be far easier to buy the cables ready made.