In my current career play, I only use space planes. In the beginning it was extremely frustrating, but, now that I understand the design principles, I enjoy it a lot more. I would post pics of my designs, but, I have not figured out how to post them to the forum. (Every time I try to post a picture it only wants another internet page) my current design is 40-60 tons with 1 mainsail and 4 whipsaws. It is super fast and gets to orbit quickly. It carries a 6T lander on its back, and a crew carrier of 4. I use it for contracts and to launch to the Mun, thus far. I dropped the mainsail and added VTOL capabilities to it, this is my Kerbal science / sight seeing machine.