After a nightly restart:

• Players will no longer be able to stealth in full plate.
• Wearing anything heavier than leather armor (> 10% Armor Penalty) will cause a penalty to stealth / increased chance to reveal (even at GM Stealth), with the chance to reveal increased based on the armor penalty of what you're wearing (see your paperdoll for armor penalty information)
• There is no penalty whatsoever for stealthing in cloth or leather.

This change has been made in order to be more in-line with UO's stealth mechanics around heavier armors.