Ballast for Bow of 2020 G21

Thanks guys for the replies. B/c of various reasons, my plan is just to manually fill and drain the bow sack this summer.

Any recommendations on other bags I might want to try to fit under the bow seats? I'm not opposed to going to a bigger bag, like say 600 pounds or even more, assuming it will fit. Or, should I just stick to the bag I posted in the link above?

Thoughts?