"Taiki wouldn't offer if he didn't mean it." At least, Tidus is sure of that, confident of the offer - wanting to back Taiki up. But he looks along the aisle they're in, rather....well, maybe big enough just for a transformation, but...

"How about we go in the gym for it? You'll have more room that way." And the his expression brightens, as if it wasn't already clear: "He flies, you know! Taiki should stretch his wings once in a while!"

A look from Inigo to Taiki. "Don't you think so?"

He has wings. Ergo, they need to exercised! Even if he's in his human body more often than not, that's got to be a consideration!