I picked up my Space Horse this past spring. I am 5'7"ish and I went with the 49cm. I was between the 49 and the 52 and I spent a lot of time riding both sizes. I really wanted to go with the 52 as the 49 just sounded wrong and looked very small, however, the 49 just felt better. If I had chosen the 52 I would've needed to shorten the stem considerably. The 49 has been great and I am happy with my decision. I am still running the stock 90mm stem but may step up to a 100mm.

Hope that helps.