Ide say tale your normal dose of each and probably just the reccomended dose of the propanolol since you are new to it and i dont believe they have any adverse interations between each other. However I AM NOT A DR so i vould be wrong and honestly you should ask your dr if you are worried about drug interactions or what your dosage should be. I personally dont see anything wrong with taking one prop with your average dose of valium but i also take things too far and have a decently high natural tolerance to benzos. Just be careful and ide wait for someone more knowledgable to reply since i really dont know much but researched it a little bit to see if there were any adverse interactions and did not find any but ide def still wait for someone else