Hi Alex,
I have built 2 poles for my self and helped build a third for others.
The first one was a compromise as we wanted it to fit in the bow of Slippery When Wet which limited the diameter but needed it to be quite long (2.8m) to get the tack far enough forward of the mast so the kite would set correctly. It worked fine for us a light weights and when single wiring. In fact when the pole bent I bore away a bit so meant we were always making good VMG. twin wiring or tight reach in lighter conditions meant that it bent opening the luff of the kite and closing the leach. This gives you more side force and less drive and backwinds the main more. I suspect you will see some of this effect and not get the full potential of the sail. A larger diameter pole and slightly shorter pole as we built for E-Numbers dosen't have this problem and provides more downwind power than we can handle. I.E. we reach a limit of righting moment or control before the pole starts bending significantly.
We used the rule of thumb that the tack needs to be about 4m in front of the mast (perhaps a bit less on a 97 rules boat and a bit moe on the 05 rules boat. For the first pole we used a byte C2 top mast section that we had spare as the mandrel, for the second we used the class pole mandrel. The pro built poles (C-tech, Ardspar) can be thinner because they use high modulus carbon. We used low modulus but i know have some medium modulus uni cloth.
