They won't hide, I got my guy at around 4", just under a month later he is now 5"+, he swims about all day, he literally never stops, never hides and always eats!
He loves floating Hikari Cichlid Gold, Mealworms, Peas, Crickets and the odd bit of Mussel that actually floats. Basically anything that will float, he eats. They have a fantastic appetite, don't worry about them not eating. It only took him a day or so to settle into eating my food.
My guy stayed in the soft water at the other end of the filter outlet for a couple of weeks, now he swims about in the current all day and never goes in the still part of the tank. HE enjoys it so much that I'm going to get him a wavemaker. It's good exercise for them!
Don't worry about them hiding! I have 8-10" aggressive cichlids in with my little guy. He doesn't care in the slightest.
Also, +1, I agree, the bigger you buy, the less likely you are to have diseases or problems. They are more hardy when they are a bit larger. I would have bought a larger one if they were available in my area.