Diazepam - 10mg adds a nice warm,sedated and relaxation of both mind and muscles.
Zolpidem - 5-10mg will add sedation, weirdness and trippiness.
Mirtazapine - Apparently very good. Not sure on doses but adds Sedation and Antihistamine action.
Cyclizine - ~50mg. As mentioned in the other thread you made, a very good Antihistamine for the job.
Promethazine - 25-50mg will add sedation and stop any nausea.
Chlorphenamine - 8-16mg adds slight sedation, good Antihistamine action and a sometimes a bit of Anxiety relief.
Quetiapine - Never tried but I'd imagine it would add
lots of sedation.
Don't overdo it on the Diazepam and Zolpidem as mixing CNS is very dangerous. And there's also the probability of leading to blackouts too which can create all sorts of problems
To be honest, I'd take 10mg of Diaz, 10mg of Zolpidem and 50mg of Cyclizine but this is with regards to
my tolerance which isn't comparable to yours.
Yours could be higher or lower so take this into consideration before you dose.
Infact it'd be worth taking only one of these at a time to see how it effects you, then, when you've tried all of them solely with your daily dose of DHC, you can add others accordingly
Be safe! And enjoy. And again, be safe (important enough to add twice).