@GK - (in case you were responding to me) - we may be talking about the same thing, but to say in another way... my avg was probably ~2@38@58 my last year in M2. Based on memory of first adjusting to 55, I don't think my avg right out of the gate would have been ~2@39@55 as a M3 skier at the next tournament. So I would have loved to stick with 58kph, pick up 6 bouys in the M3 score and hedge my bets that it would be better than the 'straight up' score I would post @55. So I'm pitting the 58kph 6 buoy bonus against the unknown buoy bonus of slowing to 55kph.
For the present, for me, this may be academic. I'm in last year of M4 ( I think....birthday 8/22/64)...but being an old-ish fogey what are the odds of skiing against other dudes opting up to 58?
But it looks like I'll be practicing 58kph this year to find out which is easier, a full pass of 35@58 or 38@55.