That's far from modern typical, which is often 72/72 is probably closer to normal. That said, if you are willing to engineer the fork and stearing, you can go as low as 68 on the head tube and gain longer wheel base and tailor stearing and load handling. The seat tube I tend to build from fundamentals of my postion, and the seat post and saddle conbination that makes sense for my kind of riding. That is normally in the 71-72 range for me.