I love my Red Tailed Shark. But they are very..... Hard to work with sometimes, I guess u could say. Having 2 is a lil Dangerous, especially in a small place, as they are very Territorial. U might want to consider finding someone you know with a nice tank that has no species of shark for one of them. or just another tank for yourself.
I have only heard of pairs of male and females getting along defending territory along side one another. and even that is just something i have Read before.
Hope my advice helps =) keep me posted on how they are doing.