Z1OwnersClub GB

hi all can anyone shed any light on the correct valve spring length on my z1.in the manual the outer is 39.3 standard but mine are 42.4 and a spare set i have are 41.are these correct and if i refit them is there a case of losing a bit of performance cos the engines having to do slightly more work to open them.
cheers

Any chance they might be APE heavy duty

no idea really just seems strange i have a set that came with other bits a few years ago and the set i pulled from the head are near enough the same