Bri and I had an admittedly somewhat lacklustre go at it a few months back with little success. Its only shale though, if you broke it up a bit with a wrecking bar or suchlike you'd soon be through providing you weren't just bringing more down on top of course.
Its a one way trip though, you couldn't get through from Rampgill without it being pre-rigged from Smallcleugh.