Drop him back in trip and if he settles going that bit quicker off an early pace then he will have more energy to use at the finish – otherwise, just let him roll from the front and see how that suits him, it wouldn’t surprise me if 5F ends up being his trip ridden that way.
There is also the possibility that he was just a very precocious mature 2 yr old that didn’t have as much developing to do from 2 to 3 and now finds that his contemporaries have simply caught up and/or surpassed him in that process.