I don't use a traditional ramp either and the entrance hole is about 30" off the ground. Instead, I installed a thick branch with a nearly-ninety degree bend in it. Essentially, it serves as a landing platform. They hop up and down easily. And I did this for the same reason -- it takes up very little space in the run compared to the long ramp I'd need otherwise. I know someone on here has their pop door hinged at the bottom and the door serves as a landing platform. I think that's also a good option.