Im not reading through this whole thread so im probably re-iterating what others are surely screaming out to you... If your burning coal stick with the clay liner period! their is no lifetime warranty on a stainless liner!!! (they will force you to pay crazy money every year to have it cleaned, they will not include re-install or removal if it does fail, its 100% their discretion if they say "opps, sir we feel you burned a lil' chunk of coal or you used a firestarter log one time and that voids your warranty"). at any rate... their is no lifetime warranty for wood or coal (they lie because your going to pay for it one way or the other).
Stick with the clay and butter it up or repair it if you need (its your best and ironically your least expensive option
would a thunk it