RE: iSonic105 technical ride
My weight is 72 kg and conditions are flat to light/medium chop in salt water bay.
If you are looking to plane early on an 8.5, iS 105 at 63.5 cm wide will probably not do as well as 77 cm wide HS 133. I would look to iS 115/125 for that. iS 115 would be best if you want it to be good with 6.5 & 8.5, iS 125 if you want earliest planing with 8.5. (Boards mag in UK tested in June 2006 issue, felt iS 115 best range was 6.5-8.5 and iS 125 was 7.0-9.0.) iS 135 would probably be okay too, but would be too big for your 6.5. But it would likely plane earlier than the 125 and for 8.5 only would probably be fine. (See Grant's thread from a few weeks back on the Star Bulletin Board raving about the early planing of his iS 135.)
I have iS 125, it is great with 8.5 and 7.3, haven't got out on it yet on 6.6.
For your smaller board for 5.5/6.5 use, I would say iS 94/101 or Kombat 97/107.
My 2 cents based on my experiences with the Starboard lineup.