The Tamrac Sling you have considered was exactly what I was going to recommend. I did however take the Velocity 9 to Tanzania and it wasn't quite the right thing for me ... I wished it had some mesh outside pockets and it was still not quite big enough for me, with my K10D, 5+ lb 300mm lens, 3 add'l lenses and 2 TCs
(11+ lbs total) ... forget about wearing it as a sling if you weigh it down like that (it's fine over one shoulder tho). But if all the gear is only a few pounds (sounds like yours is), no prob and quite comfortable.
I did read one review before buying mine of someone who's -big- and said it was too small and was very uncomfortable. I'm just under 6'2" 215lb and I have to conclude that person must have been a lot bigger ...
so just incase you are too, consider that.