By definition, Vso is in the landing configuration (depending upon who you ask, Vs1 is either clean, or in whatever configuration you're flying at the time).
Regarding speeds - the C152 POH says 60-70kts flaps up, 55-65kts flaps down. Clearly, the difference there is weight - and I think that adjusting approach speed for weight is not taught enough, or well enough. Hopefully everybody here knows how to make that correction - but in my experience most PPLs don't.
G