PG, thanks for your clarifying comments on the Rocker-Scoop line effect on planning. Someone also mentioned that sharper rails ensure quicker release that also help on early planning! I've had my doze of "banana" wave boards in the 80's which could only turn but not plan.
Your iS144 recommendations are valid, if I was supposed to jump from the light wind SL board straight to my HyperSonic 105. However, I've already acquired an RRD SL, a 120 X-Fire, which goes like a rocket from 15 knots upwards. Therefore the discussion on SL on the 6-15 knts range.
The BIG question we have been discussing is whether the same advanced sailor on the same board shape (e.g. iS144) with the same sail (e.g. OverD 9m2) in different weight classes affect how early the board will reach planning?
E.g. does a iS144 WC
plan a 2-3 knots earlier than the same iS144 Wood