As noted above the TR is tilted to provide some upward lift. The Blackhawk being slightly tail heavy. A longer tail boom would not really help as it's the CG/weight back there, not the leverage provided by the tailboom's length. The rear stabaltors actually provide lift as well, using the mainrotor downwash at a hover and changing angle for various profiles. The angle changes automatically (or manually for emergencies). The UH-60 tailrotor produces more thrust than the mainrotor on an OH-58.
The aircraft has normally a crew of 4. We would plan for a peacetime loading of 12. That's not due to wegiht (they could weigh 300lbs each or more) but the fact that there are only 12 seats. The seats themselves are designed to collapse in a crash in a more survivable way, i.e. they absorb shock. This will go a long way to letting 12 guys walk away from a hard landing. You could carry a couple more depending on how it's configured (15 IIRC), but it was easier for units to figure on squad sized units. You would always loose the extra capacity to OCs, etc. anyway.
Wartime planning was 22 people with the seats out. Obviously you loose the crash attenuation of the seats, but wartime missions are more risky and certain things become trade-offs for capability. It's not worth the risk to go without seats in peacetime. Those seats really do work. Wartime...well many times it may be safer to get more folks on the ground than make two trips.
At 22 people, the aricraft is full. Combat troops are carrying all sorts of gear, and the cabin space fills up quick. Rucksacks, weapons, etc. can take up alot of room.
The Blackhawk has more than enough power to "cube out" on the inside with people. In the UH-1H, we could run out of power before we were even close to full, depending on where you were flying.
Ross