Currently when doing singleplayer time trials there are three possible items that can be obtained; single melon, triple melon, and gold melon.
Single melons should be removed from the item pool in singleplayer. There are currently no items boxes where getting a single melon is the best possible item and there are quite a few spots where getting a single melon is effectively a run killer when it comes to trying to improve times. Are there spots where it’s not the worst? Yes, there are, but it’s never the best option and does not excuse how awful it can be compared to gold/triple melons.
By extension; I can also see the removal of the gold melon from singleplayer. While this will make certain sections of certain tracks slower the gold melon can be rather awkward to use due to its inability to be quickly discarded. However at the time of writing the removal of gold melons is not nearly as warranted as the removal of single melons.