try hurting him from the back, use the small blue cannon, it shoots both forward and backward, just place the cannon on the right side of the giant pirate with the shield.
I dont understand what I am missing.......I land perfectly, I do have all upgrades on my character and I got possition 4-5 every tima, after the first lap.....?
 "Midas' Gold Plus"){kind=icon}
 "Skeleton Pirates"){kind=icon}
 "Dillo Hills 2"){kind=icon}
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 "Defender's Quest (lengthy!) Demo"){kind=icon}
try using a bomb or a catapult, this will do the trick