Ah that old chestnut, much has been written and said about side-slipping 172s.
I believe the sideslip restriction is for 172s with 40 degree flaps (like mine) as when set they can blank the elevator. Below the 40 degree setting is ok. For those 172s with max. 30 degree flaps I believe there is a warning to avoid sideslipping due to the risk of elevator blanking.
Can anyone confirm my understanding on this?