I missed this thread when if first popped up. I have kept these fish several times. Even the tank bred ones are very skittish when they are first placed in the tank.
Mine typically hid for the first few days and then gradually became more comfortable.
They are even more shy in a lowly populated tank. For example, I just bought one a few weeks ago and he hid under a rock the entire time in the isolation tank. When placed in the community tank, he initially hid, but after seeing all the activity in the open water, he got braver.
I'm not saying you have to add more fish. I think you just have to accept that with just a few Red Fins in the tank all alone, they will tend to be shyer. If you want to bring them out more, perhaps add a peacock or a more outgoing hap?
I have also seen this happen with other Copad species (extreme shyness, particularly in a species tank holding 2-4 of them)..