I wouldn't think 3' would be too high unless they are jumping down onto rocks or concrete. At one time I had a ladder-style roost where the roosts were at 2', 4' and 6' levels and started to have issues with birds having bumble foot. I lowered the roosts to a parallel style with 4 roosts on the same level, 3' off the coop floor and haven't had any issues since.
They will roost on the highest place they can get so if you raised it, they would get up there. But if you lower it and there is nowhere higher that they can get to, they will be just as happy on the lower roost.