It also pays to not put too much material in to the classifier first off. Like about 2 shovel fills then classify, chuck out the oversize & repeat until, like you say, the catch bucket is about 3/4 full. I usually do two buckets so I can carry one in each hand, better balance, to the sluice box. By running classified material down your box you don’t need a faster water volume going down your box as you don’t have the larger rocks & stuff to wash on through. So the fine gold recovery is way better in the gentler flow & you aren’t having to manually pick out the larger rocks & stones. You also get a more gold bearing concentrated amount of lighter material to put down your box as you aren’t filling the bucket with worthless, bulk, heavier & bigger rocks & stuff that you will just chuck out at the box any way. So wasted energy & effort in carting those to the box.
JW 