Do you have the 8 speed wheel mounted already?
Asking, because I actually had trouble trying to fit just a 7 speed wheel to my PY10FC. I found it strange, cause all my other bikes that are 56cm size had no problems accommodating a 7 speed rear wheel with their 126mm spacing. I attribute it to the the PY10FC having a narrower than usual rear spacing between the rear dropouts and seat stays If you look closely at the seatstays, they actually curve inward from the top, before they hit the brake bridge, which I think give the seat stays an exagerrated angle between the brake bridge and the dropouts, making it hard to fit in 7 speeds and higher.....