RE: for Ian re:s-type 126+137
The basic rockerline template does not differ that much,especially the critical rockerflat and entry profiles are similar in template rockerline (considering varying V alters effective rockerline across/over the actual surface area - so use of "same" rockerline can be a bit debateable in one respect anyway, as two otherwise "identical" (rocker profile/template plus outline/volume/rail/thickness etc) boards could still offer noticeable differences in performance based on addition (or not) of significant V across the planing area.)
Obviously, the larger ST's make use of the increased width (and subsequent increase in surface area/s) - not just volume alone- to improve the light wind and relative early planing potential. The significant difference from ST to (say) and equivalent size (by volume and max width) iSonic is the presence of the stongly bevelled rail in the ST's, which reduces the ST's lightwind (or bigger sail/fin) performance a little, but significantly adds to the high/er wind, speed and chop ease of control, plus the ST's proven SuperX performance potential (which would not be so "easy" on a similar "sized" iSonic for example).
By comparison though, an equivalent iSonic (by volume/width) will generally offer marginally better big sail / fin handling and early planing/marginal condition performance, significantly because of the (relatively..) harder, wider rail section on the iS vs the ST.
While it's possible to run "larger than nominal" sails (fins) on the ST's to "force" their early planing (and many independent customers report good satisfaction from doing so..), we're confident that the nominated sail sizes are close to typically optimal for that range of boards.
In WA it would not be difficult to get the opportunity to test or demo an ST and/or iS to experience the subtle but real difference first hand.
Hope this answers your questions, please let us know if more info is required etc.
Cheers ~ Ian