Propranolol 2% in buffered Cetomacrogolcreme: Is this stable?

Propranolol hydrochloride has maximum stability at pH = 3. Consequently, I would not use buffered Cetomacrogol cream but the unbuffered. Dissolved In water, a 1% solution gives a pH = 5. A 2% will be slightly more acidic.

If there is no objection then we use sorbic acid as a preservative, which will also contribute to an acidic pH.  

I suspect that using the unbuffered Cetomacrogol cream we'll get a stability of 2 months. Storing in the fridge is also recommended.