I really wouldn't exceed 20mg for your first time. Zolpidem (Ambien, Stillnoct) is definitely not interchangeable with Benzodiazepines. They're so effective for insomnia because they easily render people unconscious, sometimes withing 15 minutes of swallowing the pill. For this reason, they really don't make for good drugs of abuse. All of the negative qualities of Benzodiazepines are amplified in the Z-Drugs. The potential for serious blackout is much more present with these drugs.
You can say and do anything while under the black out, so you really need to be responsible about it. People get behind the wheel of cars literally all the time on drugs like Zolpidem. They're abuse in general is worrisome to me, but what can you do.
Hide the bottle or give it to someon else after you take your dose. I'm totally serious.