What can I say ??, Screamer. you had said it all so well !!
All I could manage was that knowing
(I guess some guys would find supersonic jets, F1, rockets boring too.)
Sorry Doby, we're not trying to be harsh, but hey...
Seriously, yes, you can "loosen up" the iS with the use of faster freeride fins (slightly shorter, more raked and more base chord for a given sail size/conditions - and yes, it will be a bit more responsive and turny, won't jump a lot better and won't quite go upwind as well or as fast etc. Realistically, the iS is a dedicated and refined efficency machine built with one very clear goal of fun from performance rather than play. It's well mannered - for a slalom board- and yeah, you can through it around quite abit and it won't bite - but it's not what it was intended for either. There's a dead boring answer.
Cheers ~ Ian