My 2008 Super Kodiak came with a fastflight string. For no real reason I put a b-50 on and it shoots good. I have no experience with fastflight strings. Will I see any difference in changing to fastflight? I know I'll loose some speed  but if I want speed I'd go 30-06.
60# pull
28.5" arrows pulling 28"
2016 arrows with 125gr points
1/4 nock getting good flight feathered and bareshaft

its true you will get a bit more speed with a ff string but the real advantage is quietness and less shock(design dependant)   Also  personally I love BCY X  i never had to adjust the brace depending on temperature.

Unless I'm mistaken it was shipped with a 14 strand Dynaflight '97 string.  Where high performance materials really shine is they are much more durable, can reduce shock, are more consistent, and have much less stretch/creep.  Blended materials like BCY-X are even more consistent in varying temps, especially when it's hot.

I've tuned with B-50   Is Fastflight gonna change this greatly????

Might show a little weak? Personally I am not a B-50 fan, stretches to much at times you don't want it to. Not a fan of D-97 either. To noisy, I don't like a lot of "balls" on my strings and IME I needed that to quite a Bear TD. I like BCY X and have it on all my Bears including a SK.

Depends on several things.  Probably will change is some, but how much will vary with the build, strand count, nock fit, etc.

Recently installed a skinny high perform and string on my 72" recurve. Looks great and adds some stroke. However dug into my fingers like something fierce with a heavy bow. Ordered a b55 Flemish and itsvmuch more easy on my fingers.

Put a SBD D10 or a ten rings string on it with Allan's material and you'll never go back to B50 or 55 again .it will be a different bow,all for the good.

IMO, I wouldn't get hung up on "skinny".  Every controlled test I know of (Hooter Shooter and chronograph)  showed very little if any performance gain, plus you loose stability, consistency, and durability...all the big benefits you get from these materials to begin with.  I'm no Rod Jenkins, but I have tried them off and on for the past 20 years...can't find any real benefit.  Black Widow had a challenge out a few years ago offering a free bow if someone could show a gain of...I think it was 4 fps with their string vs. BW's standard 14 strand Dynaflight '97.  The "catch" was if your string didn't show that gain, you had to buy a bow at regular cost.  To the best of my knowledge nobody even tried.

Material-wise, the quietest (before tuning) has always been blended materials...450+, BCY-X, and now X-99.  They will also be the most stable in higher temperatures.

Course everyone has their preferances.  YMMV

Always wanted a super kodiak and will pick one up someday, so good info.
Shooting a bear Griz now and it's packed w mojo so hard to out it down. 
Tim B