Should workout since they are both on the high end of the agression scale. Both can really shell it out and hold their own.
To me, this is an argument against it working. I understand what you're saying, and in a bigger tank this would be a better argument, but in such a small tank I feel this would turn into a war until only one was left standing.
This COULD work, but I wouldn't advise putting a full-grown Con in a 29 with a full-grown jewel.