Tryin' is spot on IMO. I initially bought a 250 cm for the first solo I built and after learning to use it, thought it was the best. Then I started making them ... moving through a 260 cm, better, then a 270 cm, better again.
I figure for my ~6" frame, the current boat at 26.5 " at the gunnels, 270 cm is about the sweet spot ... I am however building another paddle batch this summer and those will be 280 cm ... by request from friends and curiosity for mine.