Eric Marshack has numbers that work for him that are in my A-class ballpark too: I have 4 carbon masts, some of which are not yet broken.

See Landenberger-sailing.com Tuning guide A-class 2005. Landy describes that you have to match sail luffcurve to mast, mast prebend, downhaul, spreader rake, diamond wire tension: And know why all of these interact to be correct.

Briefly- 33-37 (max in a blow) on the Loos guage with usual twisted wire diamonds- these #s change with dyform, and change more with solid wire rigging.