Messed up and put the wrong number of holes into the calculator and now have a set of 258mm spokes instead of 254mm. How much difference will this make?

CRC wont accept spokes on return so I either need to shell out for some more & try and flog these ones or try and make it work.

Wheel builders its over to you

depends on the nipples – you can always get more thread cut on them if there won't be enough to hold the extra 4mm of spoke… it's not like they'll be long enough to effect anything else – bit of extra rotating weight perhaps?

or just buy some more spokes…

or do a fancy pattern!?

they might poke through the rim.

they'll probably bind on the nipples. if it's 36 spoke would they fit if you built it 4 cross?