Stats:
Cargo Size: 2.5 Meters, about half a "Jumbo" Tank long
Cargo Capacity: ~20 tons (I have only tested up to 18 tons, but I assume it can go a bit higher)
Crew Capacity: 4
Boosters: 4 SRBs each with two NASA SRBs clipped together
OMS: 2 NERVA Engines
Price: 240,200

Information:
Explaining everything about this craft is rather difficult, so I will just tell you the basics on how to fly it: First the engines, each booster (there are 4, Buran style) includes 2 of the NASA SRBs clipped together. The external fuel tank has 1 of those 4 engine cluster things. The external fuel tank engine will need to be manually controlled during the flight. The Orbiter has 2 "Skipper" engines, they have a thrust setting of 74%, this thrust setting is meant for an empty cargo bay, so I highly recommend increasing this before launch when lifting a heavy payload. During launch, let the SAS do the flying, it is very important to watch the pitch indicator. As the rocket becomes unbalanced (as it drains fuel), the SAS will compensate with pitch input. Basically, when the pitch indicator nears full pitch, the SAS is basically saying: "I can't hold it much longer, do something!" This is when you need to adjust ET's (external fuel tank) thrust. I reccomend keeping the window for that engine open during the whole launch.

Now some info on the cargo bay: The doors work by undocking from the shuttle, but they are held in place by some structural things, so hey shouldn't float away (hopefully). Once undocked, you can switch focus to them ([/]), and then open/close them with the yaw controls. Since they are now separate crafts, DO NOT timewarp, exit to the KSC Menu, focus on a craft over 2.5 Km away, etc. Close them first. When closing the doors, simply rotate them back to the docking ports. Note that there are docking ports in BOTH the front and back of each door. Sometimes the back ports may not dock, if this happens, try opening and closing them again. Leaving the door's SAS off seems to help with this.

The cockpit lights can be toggled with "5." The main cockpit is tilted down 5 degrees, this helps the pilots see out the windows during landing. Also there is extra crew storage below the cockpit in a MK2 Crew container. It is only accessible with the crew transfer, so you will have to clip the camera into the nose to click the hatch and enable crew transfer (You CAN just click "EVA," but warranty void if you do this).

Action Groups:
1: Toggle Two Main "Skipper" thrusters
2: Toggle OMS NERVAs
3: Undock cargo bay doors (usually needs to be pressed twice to fully undock)
4: Open/Close Docking Port (Located Under Cockpit)
5: Cockpit Lights (Because why not?)
Abort: This shuttle actually has an abort! Deploys some parachutes attached to the main Cockpit. Kerbals in lower passenger cabin = Dead. Rest of shuttle = KABOOM! Yay safety!

Launch Instructions:
1) Set 2 "Skipper" engines to appropriate thrust setting (74% for by default for no cargo, 100% for 15 tons and above, 18 tons and above you may need to turn the thrust down on the ETs Engine)
2) Make sure payload is secure (warranty void if you don't do this!!!)
3) Throttle up, when throttle reaches 50%, press "space" to active main engines.
4) At 100% throttle, press "space" again to launch!
5) At 100 m, do a roll program (roll shuttle so "up" is east/whatever direction you're launching in).
6) When the shuttle starts to pitch up too much, tweak the ET's (external fuel tank) engine to a lower thrust (You will need to constantly watch the tilt and keep this engine at the right setting).
7) When the first set of SRBs run out, be sure to quickly throttle up the ETs engine to hold position.
8) At 10 Km begin gravity turn and hold 45 degrees by the time you reach 15 Km.
9) When the SRBs fully run out press space to stage them off. Again remember to throttle up the ET.
11) When the apoapsis is 30 Km, pitch to 50 degrees (from vertical).
12) When the apoapsis is 40 Km, pitch to 60 degrees.
13) When the apoapsis is 55 Km, pitch to 85 degrees.
14) When the apoapsis is 60 Km, level off.
15) When the periapsis is about to become 20 Km (around 22 km is when debris get deleted), jettison the external fuel tank (if you haven't already), or you can keep going if you need some extra delta-V.
16) Staging the ET will activate the OMS engines, press "1" to shut down the now fuel-less "Skippers."
17) Float to apoapsis and circularize.
17) Orbit! Do whatever you want now.

Landing:
1) Deorbit somewhere that will get you to KSC
2) During re-entry, maneuver the shuttle to land at KSC
3) Once the flames stop, pitch down to 45 degrees (A VERRRRY steep descent path) (Blame KSP's terrible aerodynamic model for that). Basically, dive toward the runway.
4) If night, turn on the landing lights.
5) About 100 meters above ground, PULL UP! If this is done correctly, you should touch down at about 55 m/s, and not crash. If done incorrectly, expect lots of explosions, press "backspace" or the Abort button on your HUD if you see explosions and slam the brakes.

Please see this forum thread or comments and questions:

http://forum.kerbalspaceprogram.com/threads/96502-Zephyr-STS-Stock-Space-Shuttle-w-2-5-meter-Cargo-Bay

[Stock] Zephyr STS-Stock Space Shuttle w/ 2.5 meter Cargo Bay