Many species are adaptible, but remember Corys come from soft or very soft waters of south America. First of all, a fish shouldnt only survive, but also thrive.
Species ability to survive different ph values vary. Some are very sensitive, and others adapt, but it is no good thing to put extra stress on living organisms. Personally I would choose only fishes that were adapted to the conditions I could offer.
In several countries there are rising standards and discussions on life forms in aquariums, and ethics relating to this. Germany has a standard on how fish should be kept, and I know Norway has that discussion as well.
If an organism is put into the wrong ph, iones and particles in the organism will not act normally. If a plant is put into soil of the wrong ph, it will easily loose its roots, and rot. Growth will slow down, and you will have to expect the worst. Maybe a reddish stress-colour will show. So also with fish; you might see skin damages, and diseases and and parasites will have easier access, as the organisms immune system is not as strong as it should be.
We, the aquarists (human beings) are the ones responsible for keeping life forms under artificial conditions. We do have a responsibility to do our best to give those animals the best conditions, that are close enough to their requirements.
The cory relative Hoplosternum is said to be very adaptible, and my Baensch lexicon states up to ph 8,3 and dGH 30. There are some Synodontis species from Lake Tanganyika and thereabouts, that are adapted to high ph: S. granulosus (to 25cm/10inches), S. petricola (11cm/4inches), S. polli (Polls upside-down catfish 15cm/6inches).
Where I live now, the water is very hard, and I have to use rainwater all the time for my corys.. Now in winter, I have to store rainwater in large cans..
Good luck with your fish!
but being a former Dentonite and UNT employee your name caught my eye!