Surely if the valve length is the same and there are matching springs and collet washer it shouldnt matter really. I would put on the pb dual springs and collet washer if the collets are the same groove style for the different valves. I still don't see where the gains are to be had. Guide work wasn't cheap when I had it done. £5 a valve guide plus £5 for them to be honed plus vat. That's £50 to fit valves with a slightly thinner shaft.