How much does he weigh? The HRS recommends 1 tablespoon per kilo bun for healthy adult buns. Cutting back further wont harm his health provided he eats a good amount of hay. To keep him from starving himself, you could perhaps divide the daily ration up into two servings, unless you’re doing that already, of course.
Giz is a big rabbit, which of course makes it difficult to weigh him at home. If he’s a good weight, you’ll need to keep an eye so he doesn’t lose too much weight since pellets are very calorie dense and cutting back reduces the daily caloric intake significantly.
Some buns are prone to sticky poop. It doesn’t seem to affect their quality of life very much, but it’s of course inconvenient for the human.
Sometimes sticky poop is a matter of the bun not being able to reach his cecotropes or clean himself, it can also be about not being able to notice when there are cecotropes due to impaired nerve signalling.