I think the food itself is worth considering. I am currently using reef jerky which is the product that avast sells but I find that it's much more buoyant than my flakes which is what I typically use.
Here is my attempt to solve the original problem outline by op.
I basically extended the size of the plank using a 2" coupler and another 2" pipe cut the same length of the original tub that comes with the plank. This solved two things for me. It drops the food closer to my return pump pretty much guaranteeing my return pump sucks it into the display and also provides more time for the food to soak in the water before it gets sucked into the bottom of the plank. I find it works better but again the reef jerky is super bouyant and I still see a good amount floating on the surface.
I've only tested a few feedings like this but seems to work much better so far.
Here is my attempt to solve the original problem outline by op.
I basically extended the size of the plank using a 2" coupler and another 2" pipe cut the same length of the original tub that comes with the plank. This solved two things for me. It drops the food closer to my return pump pretty much guaranteeing my return pump sucks it into the display and also provides more time for the food to soak in the water before it gets sucked into the bottom of the plank. I find it works better but again the reef jerky is super bouyant and I still see a good amount floating on the surface.
I've only tested a few feedings like this but seems to work much better so far.

