Clone of Viper Mk2 from Battlestar Galactica
Will do SSTO and return to KSP.
Has probe core and 5x Docking Ports to enable external tanks, equipment packs
It also has a Grapple to dock to the side of ships, due to the lack of magnetic skids.
It's extremely sensitive on takeoff, so adopt 5-10degrees angle of attack and leave it there, otherwise you won't get the nose up again and achieve orbit.
2x Puff engines will give extra boost to chase down raiders etc.
Action groups as follows.
1. Toggle RAPIERs/Intakes between air breathing and closed cycle
2. Toggle rapiers on and off
3. Toggle Grapple
4. Toggle docking port
5. Toggle Puff engines
Handles like a jackrabbit, and is easy to do high angle of attack manouvers with lower fuel.
Craft file is here on kerbalx
https://kerbalx.com/atassiedevil/Viper-Mk2
Enjoy!