What sort of incompetent fool teaches 80 kts as the approach speed for a PA28-140? No wonder some people have difficulty landing!
We use a full-flap approach speed of 70mph for a Cherokee 140C and 65kts for a Warrior (yes - it should be 63 but people find it easier to keep the needle midway between 60 and 70! I'll allow them a 2 kt error!). Both are valid for max weight; no adding 5 kts for Mum, no adding 5 kts 'because of the wind' - just use the correct figures and landing is a doddle!