Grizz was/is everything Kappa described IMO, but was also a very good teacher. He posted a thread a while before he "left", about how to make snap shops with the Mk108 in the K4, it's probably one of the best examples of explaining how to shoot anything, let alone the 30mm, in the game. Great example of adult learning/teaching techniques, I'll have to find the thread and link it later.
17 kills is a lot, but nothing impossible. I will say that since 2010 or so when I started flying a bit again, that compared to early days, say 99 to 2004ish, getting high kill streaks is much, much more difficult now. I have films/screens of a number of 20+ streaks I had (with rearms obviously) in everything from the Spit5 to the F4U4. In the last 7 years I don't think I've cracked double digits, not once. Maybe it's a better overall skill level, even if statistically it doesn't really show that as per Snailman graphs and so on - or maybe I'm just getting worse.
I don't think the Grizz 262 video will ever be topped, and will stand as the longest streak with proof forever.