I put a lowered seat on my K6. I can now put both feet flat on the floor (i'm 5'6"). I think the 'official' measurement is 20mm lower. It didn't feel uncomfortable for me and I rode from Hartlepool, down to Hemel Hempstead (around 230miles) then back again and I didn't find it any better or worse comfort wise than the original seat.
Hope that helps a bit.
