Fir bark uneven moisture level

[MrHungx]

I grow my cattleya alliance orchids in plastic pots with medium grade for bark with a top dressing of sphagnum moss. I water my cattleyas in the morning and the sphagnum moss is dry by evening. I find that the top half of the medium in the pot is usually bone dry and the bottom half is very moist. As such, I tend to underwater out of fear of rotting the roots. However, the new growths tend to be smaller and not as developed as the older pseudobulbs. How can I make the medium dry out more evenly? I'm considering switching to a sphagnum moss/bark mixture as this currently works well with my other orchids.