We were not on a 24 seater-- I'll have to ask my husband what type of planes they were.

Honestly I think that they routinely ask everyone to check their carry ons! Yes, we were asked to check our carry ons as we boarded the plane. Our bags were normal carry on size and were not unusually heavy. I did not see the airlines weigh anyone's carry on on either flight. When we told them that the bags contained valuables and we were advised not to check them on, the airlines backed off immediately. And as I indicated, there was plenty of room on the plane to store the luggage so it was absolutely no problem.

We just returned from SA over the weekend (trip report to follow in a few days). I too had lots of camera equipment and was concerned about weight restrictions for carry-on. I used a Kiboko bag (love it!) and had ~32 lbs of gear in it. We flew 4 flights on SAA (JFK - JNB, JNB - CPT, CPT - JNB and JNB - JFK) -- the only time someone asked to weigh my carry on was JNB - JFK. I pretended to not understand and kept walking. He didn't care enough to follow up.

Checked with my hubby... we were on a Boeing 737 from Kruger to Cape Town and from Cape Town to Johannesburg.

One of our flights was a 24 seater--from Upington to JNB. My Lowepro Computrekker would not fit in the overhead but fit easily under the seat. At no time did I see anyone's carry-on weighed or questioned (and I was watching because I was concerned--mine weighed at least 25 lbs.)

Just back from another trip to Zambia and flew SAA a few times. They didn't weight the carryons but at one of the checkpoints there was a SAA guy asking people to put their carry on luggage into the size checker. I wore a large camera backpack that wouldn't fit and gave him my small bag. When he saw that I had a backpack, I just ignored him (like on of the other posters) and he didn't care enough to chase me down. So my suggestion would not to show the ticket gate your oversized carryon, ignore the size checker guy at the checkpoint and you will be fine.