I really enjoyed using my Hug-a-Bub sling, but once DS2 hit 10kg (at about
8mo) the building of his organisational skills had to give way to the
incipient destruction of my knee joints! I'm not a very big person and found
that a few hours of shopping and slinging led to sleeplessness from knee pain.

I started having knee issues (and shoulder, too) with my OTSBH sling.
I love that sling, but my 23 lb, 8 mo was getting too heavy to be
supported so much on one shoulder - the opposite knee really took a
beating. But, then I got an Ergo - and, I can see a dramatic
improvement. I still use the OTSBH sling for nursing to sleep, but the
Ergo works great out and about.

I can't think of a safe way to sling a baby when I'm cooking. Particularly a
grabby baby!

Wearing my baby on the back is a good compromise. But, I'd be hesitant
still to wear her I were cooking something like hot oil. With
preparing salads, rice dishes, etc, I don't see a safety issue with her
on the back.