The one engine challenge

[Pete-]

Due to recent events, Kerbin has a major engine manufacturing problem. So new regulations are in place, limiting the number of engines of any space craft to only one. 

Of course, the space program must continue, so here's where you come in:

• Get a manned spacecraft into stable orbit with the most DV left
• The craft can only have one engine on it.
• Stock parts only
• Mods that give information about the dv you have left allowed.

The score will be the dv you have left in orbit.

Bonus kudos if you manage to land on the mun, minmus, or another planet and safely get back to Kerbin. If you do so, you can use RCS thrusters for landing stability control only.

My simple first attempt at 2959 m/s left, in a bit suboptimal orbit.

 

[Jetski]

2971 in orbit with a single Rhino.  Enough to get to Dres and back.  I'm thinking a spaceplane might have better results here?  Using wing lift and drop tanks maybe, so a low-TWR start isn't as much of a hassle.