G5 Stamina is just narrative tax, no consistent at all.
His Round 1 vs. Imunko he used a mere Dawn Gatlin and was already hellla drained, considering he ate at the party and later with Loki again.
Now that he is eating some more, he will have Kaido's stamina in order to deal with Imu.
Shit is cheap and ridiculous
But anyway, where the fuck is the raws