I came to the thread to post a jokey "probably when I'm dead" response... but then OP said the guy was talking about BMW K's, so my ears pricked up and I went off to have a skim read... if one can skim read with pricked up ears...
Well, he starts off well, with saying he's talking about
Sports
Tourers, but why
@Sadlsor you thought that might not apply to
ST1300's is beyond me.
Then he says you sit in, and not on K's... and he's right, but then we get into the "if you're within the air bubble behind the ST screen, are you in the bike or on it?" Still, you do sit
more in a K than an ST.
Then he says that sports bikes
require you to get your butt moving around, and that's the point that he lost me. I've ridden many sports bikes, many super sports bikes, and I'm yet to find one that
requires me to do anything if I'd rather not. Sure, if I want to keep a bike more upright and not risk grounding out on the pegs, I'll wiggle my butt appropriately... but those times are
rare.
So now that I got bored of reading that article, my genuine answer, figure out what's comfortable
for you, be vaguely hydrated, fed, and mentally engaged with what's happening, and you
probably won't fall asleep while riding.