I just did a lot of research for a different but related question and while doing so discovered something which I would like confirmed:
We are all familiar with how enlarge person works, and how it cant be stacked with other size increasing magics.
During my research I came across the transmutation spell Legendary Proportions which does not have that line.
So if you were to have the polymorph spell cast on you first, and then the transmutation spell, would this not make you gargantuan?
Bear in mind that none of the listed spells contain the type of ruling which states different magical size increases do not stack, those are specific to spells, I cant find an outside spell description ruling stating this. Since legendary proportions is not a polymorph, it doesnt interact with the ruling for how you can only be under the effect of one polymorph spell.
So, would you become a gargantuan humanoid or is there a rule somewhere that I have not found?