all day touring, no problem and yes, it does depend on how you sit, using core, ass & thighs instead of just leaning on wrists, but also how you fit the bike, how fit you are etc. Works for me, but I'm not tall.
L1 awesome, had a very memorable weekend with one, but not sure I'd fancy it two-up, or that a pillion would either. Not enough mass, grunt, stability to lend itself to the smooth progress a pillion might enjoy. Less highly tuned middleweights, like your own bandit, (or bigger engined sportsbikes) are probably a better bet for two-up work.
Anything can go on track, especially something like an SV650, or a bandit 1250 makes a really useful tourer with a fair bit of get up and go.
Some insurers won't even insure a sportsbike for riding two-up any more, so check it out.