RE: Ola - Harness line length
Not Ola H. here, but I'm somewhat similar in height as you (173cm) so I thought I would comment on what I use. However, it's important to consider one's arm length too. My arms are on the shorter side at a 32" shirt sleeve length. As a result I like 24" lines, and I always use a seat harness. Many years ago I used up to 26" lines, but in those days the spread between attachment points was generally much greater than recommended today.
Although there is a line of thought that coincides with Doby's size range recommendation, I know that it wouldn't work for me because my arms are quite extended when I sail. Yet, if I recollect correctly, I think Kevin Pritchard and Phil McGain use lines in the 28-32" range, and KP recently indicated that he always uses a waist harness these days. But that doesn't surprise me, as both of these guys are much taller than me.
One thing that you might do is check whether one of your local shops has an active set-up that allows one to test different harnesses in a dynamic way. The Windance shop in the Columbia Gorge has one, that consisted of single boom arm (with a harness line attached) that was tied off with rope on a stationary object, and it included a platform you would stand on that incorporated a one sided set of footstraps to lock into. By experimenting with different line lengths you could readily find your ideal length.