RE: Start centerboard?
Can you tell us which of the above center fins (probably #1 or #2) you have in your 2 Start boards?
I mostly used the stock (OEM) rear fin in the center fin slot, and then put a True Ames 38 cm Shallow water fin in the rear slot.
Others have used a very small fin in the rear slot and the stock rear fin in the middle.
Astually a small slalom fin (like the 42 cm that came with the original 105 Hypersonic, proved to be the best setup. Not so long that the students could not do beachstarts, and pretty good for shallower waters, but much better upwnd than either "1 or #2 above.
And, as discussed on your post to the other forum, there could be some significant technique issues here as well.
Hope this helps,