Not an expert, but I heard that benzos can sometimes take up to 2 hours to take effect, although it varies with each person.
So to be safe, perhaps you should take some 2 hours prior to SN, then take a bit more half an hour later, etc.....
example.... suppose you were taking SN at 16:00, then :
14:00 take some benzo
14:30 take some more benzo
15:00 take some more benzo
15:30 take final benzo
16:00 take SN
Note : this is just my "guess" at a method, as stated, I'm no expert....
Someone who knows more than me might say this is a bad idea, so please don't "rely" on my suggestion, but make your own assessment.....
I suppose you want to find a balance and not become so tired that you fall asleep before taking the SN.....
Although in that case you can always try again when you wake up.....