When I create a Flip Fluid tank and just a add a simple cube above it (I was just testing things.) I made the cube a rigid body object and then played the sim. First the cube falls straight through the water. (It collides, but just falls down all the way to infinity.)I'm pretty sure it should go in a little then splash back out. Anyway I messed with the density of the fluid AND the box and nothing worked. I made the object a hero object. Still the same. When the two simulation objects merge in the AUTODOP network. I flipped those around and it changed the sim even though it was on mutual relationship. Now the box barely touches the fluid (does not go in) and then the water explodes everywhere. I messed with the density and I still cannot get the box to realistically dip into the water a bit and then splash back out like normal. Yes, the feedback on the DOP network is on 2. So not sure what the problem is.

Sometimes it is just easier to rebuild setups than to debug them. Especially when they are simple like this. I deleted all the nodes, kept the cube and created a FLIP tank, default settings. The I selected the cube and used the Hero RBD button. I dove inside the DOPNetwork and set the Feedback scale to 1.