Space planes in RSS with FAR?

So, I've been trying my hand at RSS and I'm loving. Having to spend a lot of effort into any planetary mission other than a tiny is great.

However, I also love space planes in stock. I just can't get seem to get a space plane working with a larger Kerbin. Getting to space is easy, but circularizing once I'm up there is nearly impossible, I find myself needing 4000+ m/s of delta v, which is nearly impossible with an SSTO spaceplane.

So does anyone have any advice or hints to give?