Chelsio cards, jumbo frames, memory fragmentation and performance in FreeBSD 13.x?

Pretty close to two years ago, we tripped across conditions where heavily
used FreeBSD 11.x packet-filter firewalls would slow to a crawl and load
would go crazy.

In a fit of hopefulness with our upgrade to FreeBSD 13.0, I removed the
hw.cxgbe.largest_rx_cluster settings we put in place -- only to have our
hardest hit firewall experience high load and plummeting bandwidth within a
few hours.

So, I have two questions -- is there a better fix for this? Or, is the
approach to set largest_rx_cluster to 4k and move on?

Thanks in advance!