If possible I'd do a test before the speech. I can take 40mg of Propranolol it works pretty quickly (about 20 mins) but I'm small, about 7 stone in weight. It does stop the physical symptoms, signs of anxiety outwardly like sweating, heart racing and trembling because it's lowering your blood pressure, that people would notice which slightly helps your head stay in control of your nerves because you know other people can't actually see what's going on. I'm told 120mg, so 3 times a day is okay if necessary. I rarely use it at all. The Valium dose is shocking, but that is shocking to me (personal opinion) I thought 10mg was really high. So I like the others have said would be very cautious you don't collapse or slur your speech. They put me on Propranolol when they just stopped by low valium dose which was 6mg tops per day. Mixing the two does not seem sensible. Like I said before I'd try a trial run with just 1 40mg prop. Certainly agree with getting that valium dose under control because valium can backfire and increase the symptoms it was supposed to be controlling. As a matter of interest was the prop prescribed to you by a Dr who is aware of your valium dosage?...Makes me wonder why you'd need both. When I took Prop once and was still on valium I recall feeling really sick and never mixed the two drugs together again.