your average "weekend warrior" may struggle to keep within +/- 5kts
Apart from being frightfully condecending the simple answer is that pilots should learn to be hard on themselves and try to achieve exactly the right speeds/altitudes whatever. Set some targets and keep to them. That is part of the challenge of flying.
Terrorhawks and 152 cannot bite unless grossly mishandled (they are aircraft that can
only just kill you!). They are nothing other than massively docile trainers - that applies to the whole flight envelope. Bar stories spring up about "...there I was, this dratted 152 was evil, I tell you..." - For goodness' sake!
This discussion is nothing like m/way speed limits. What a perverse way of describing it. We are not specifically talking about flying accurately - more about using the correct speeds in the first place (before any sloppiness is accounted for).
Stearmen (?) and Citations, indeed! Help me, please. I want a flying club where we teach people to fly the aeroplane that they are actually sitting in rather than the one the instructor wants to be sitting in. Arrrgh!