I just uploaded version 2.6 with changes to Alteration flesh spells and Dragonhide.
http://skyrim.nexusmods.com/downloads/file.php?id=11139
Flesh spells will now drain magicka whenever the caster is hit in combat. Stronger spells will drain more. This will hopefully add a nice mechanic to armor spells, making them to have a kind of "upkeep" that only comes in play when you actually use your defenses. When facing hard hitting monsters, the most powerful available armor will probably be welcome even if that means draining more magicka when hit, since otherwise you can simply die. But when facing weaker mobs, casting only, say, Oakflesh may be the best idea, saving magicka for offense.
So, with maxed Mage Armor mages will be able to have pretty nice armor rating wearing cloth, but that will toss perks and resources during combat.
Dragonhide will now add damage reduction that can stack with armor, so you can have your normal armor spell running and cast Dragonhide just before a tough fight for additional protection, while the armor will still keep running.
Feedback, specially regarding the amount of magicka drained per hit, would be great
