Re the 30 deg full flap mod on the 152, I think you'll find this has more to do with product liability claims than anything else - a 150 doesn't go far with 40 degrees down.
Remember the 150 was 100hp, the 152 112hp (108hp in the latter ones with the O-235 N2C fitted in place of the L2C - supposed to help prevent lead fouling of the plugs by a change in the combustion chamber design - it didn't work!). The 152 airframe was pretty much the same as the last 150Ms but with 28V electrics and the engine change.
The 172P onwards was also limited to 30 degrees maximum flap.