Search for bimix on the site and you will see a few threads that deal with this topic.
Most seem to end up at somewhere between 0.25ml and 0.5ml when using 30/1 bimix, so I opted to start at 0.2ml for the trial run, then bump it up 0.05ml each time.
I am about to try a watered down trimix in a couple of days. Vial arrived today. I had the urologist order a watered down trimix formula (only 2.5 mcg of alprostadil) so I could test the "pain/aching" waters sometimes associated with alprostadil. Depending upon how that goes, I might up it to 5 mcg alprostadil, etc....but I digress....lol.