Find minimum (realistic) size of elastic buffers experimentally

[martijnbastiaan]

After merging #580 we measure UGNs (and IGNs). We're interested in finding out how small we can make the elastic buffers without jeopardizing a system's stability (after convergence).

Our current vendor IP "only" allows FIFOs to be scaled back to ~16 elements, so we might need to make the "middle" of the FIFO configurable.