Why don't you give it a try with the iSonic101 or 105. The iS125 is a very nice board as you menton. I have surfed an iS105 and this board really handles a huge wind- and sailrange. I have sailed it with an Overdrive 7.5 and with my 95 kg's this was perfectly in balance. It feeled like I could go even bigger, only the minor volume of this board may give limitations in deep water and powerless winds. I also surfed the iS105 with stronger winds suitable for 6.0 mtr, but then the Sonic 85 is easier to surf if winds are very steady. I never sailed the S-type, it really may have some advantages over the iS, but the big advance of the iS105,101over the S-type according to what I heared is that the iS handle big sails (+7 mtr) whith much more ease and balance

.