jtill wrote:
Big plants
that I have re-potted, two, had short roots, about 6", most stopped at
4". Normal?

Probably not normal. That sounds like a cultural problem, possibly
decomposed media, too wet, and/or insufficient oxygen in the pot. A
large well established Cattleya (and most other orchids) should have
long, branching roots penetrating all the way to the bottom of the pot.
Failure of the roots to penetrate the media suggests that the plant
wasn't very happy and may prefer different media mounting. I've
occasionally received plants with very short roots from nurseries that
don't repot frequently enough. If the nursery is humid and they water
frequently, you can have an apparently healthy plant with short stubby
roots at the surface of the pot. When I repot such plants into more
suitable mixes, they usually produce a more vigorous root system.

Some cattleyas just don't seem to like pots and will grow much better
roots on a mount.

In general, a taller pot will drain better than a short wide pot, and
the roots will get more oxygen. For S/H, I'd think that you definitely
want a pot that is taller than it is wide.

Nick