Could go either way since we have little idea of what 40% Daimao's limit was, making him anywhere from Multi-City Block level to Large Town/Small City level. On the lowest end, Luffy may stomp in base alone from Alabasta and onwards, whilst at the high end Daimao would stomp. I'd probably lean closer to the lower end for Daimao's 40% self, so Luffy wins without much trouble.