I've had minimal experience with barbs and coreys but my barbs never picked on my dojo loach and my coreys never bothered anything more than an inch or two above the substrate. I don't think they would be any trouble for eachother but, I have been wrong in the past.
should be - they dwell at very different levels. not sure if you shouldn't maybe put 1 or 2 more barbs in there to contain any aggression within the school. also not sure if that would be pushing it in a 29g. perhaps someone else could help there.
well, i have only 3 tiger barbs (4 have died over the years, never got anymore) and 6 cories and my tiger barbs could care less about the cories in my opinion. they never bother the cories and i mean never. the cories swim around the bottom levels and the tigers swim around the middle to top levels so really, its not an issue at all. I'd say go for it, cories are amazing and have awesome personalities. Even though my skunks all look the same, there is two that i can tell the difference between the rest of them because of there personalities! you'll love them! as for wondering if you would be over stocking your tank...i think that i would get the 6 cories (or maybe just 5), but cut the harleys down to 5 or 6. I believe they are schoolers so 5 or 6 of them would still be enough for them to be comfortable and a good amount to get. Even if this did overstock your tank a little bit, just keep up with the water changes and regular maintenance. I mean, i'm not gonna lie, my 50g. is a tad overstocked but you'd never know it judging on my fishes wellness. They're all healthy and happy (i'd like to think they are happy) and doing fine even though it is a little overstocked. I just do my regular maintenance and test the water often and everything is good!
I think the Cories and the Tiger Barbs will get along just fine. In fact, I might add 2-3 more barbs, just to make sure they have plenty of each other to pick on. (TBs are at their worst behavior when there are only one or two in a tank, I think.)
The Cories won't even notice them, but you might want to give them some hiding places, just in case.