Combining an island attack +, while keeping an island in the air and moving it to the capital, it is as if KAIDO "almost" made / performed two island level attacks at the same time. And counting on his huge list of tank blows, and the energy expenditure of his HAKAI and his DF, with the island, he still hasn't even made a "HUFF".
Kaido had great feats this chapter, but lifting Onigashima is not ones of them. Lifting Onigashima (like Doffy's Bird Cage) doesn't seem to tax him at all. There's no indication that it's in any way, shape or form hampering his combat ability.
We can wank Kaido without reaching to such an extent.