Our front amp gal, Joshi, has no issues going up or down our 13 steps.
She is not a tall leggy greyhound, so the center of balance is a bit lower. She's about 45 pounds. Saluki/GSDx.
She goes up very slowly - one step at a time. I think it takes a lot of abs to lift the front leg up, then one-at-a-time the back legs. Rinse and repeat. It's slow.
Going down is pretty fast... Hop Hop Hop.
Our previous front-amp boy was smaller and a senior, but he did the stairs just like Joshi.