Perhaps draw a VG diagram on an infamous whiteboard and lable the areas "within design stress tolerances", "bend" & "break". Then use L=Cl x 1/2 x p x Vsquared x S

where L=lift Cl= coefficient of lift p=airdensity V=velocity S=wing area

to demonstrated the "squared" relationship between speed & lift; ie: trebling the speed begets nine times the lift.

Since stall speeds in the POH are generally given for max weight conditions; if we're flying at weights less than gross, the stall speed & maneuvering speed will be less.

For an example lets use a PA28R-200

Max gross weight of 2650 lbs. Va=114 kts

For this example use the following loading.

BEW=1613, Pilot=170, pax=160, bags=20, fuel=204 for a total of 2167 lbs.

2167/2650=.817 or, 81.7% of max gross

to get .817 times as much lift, find the square root of .817 which is .904 or 90.4% rounded to 90%; meaning we only need 90% of the airspeed required at max gross.

Ergo, Va at 2167 lbs = .90 x 114 kts = 102.6 kts or 103 kts.