You mean the custom item creation guidelines, which you're proving why they're guidelines by virtue of this thread's existence...Assorted Magic Items (AKA abusing item creation rules)
Thank you! Will definitely use as a source for the future.
Two of the same benefit from the same source don't stack, and instead overlap. If a Goliath put on the ring, it wouldn't do anything until he was reincarnated into a Kobold, at which point it would apply as normal.
"1/2 size increase" is not a term. Thus the "0.5 + 0.5 = 1" logic (that I think you are using) does not apply.