I was hoping somebody would suggest that (and eventually try it out).

With TB5, and deep pockets, you might probably also benchmark it against a setup with dedicated TB5 enclosures (e.g., Mercury Helios 5S).

TB5 has PCIe 4.0 x4 instead of PCIe 3.0 x4 -- that should give you 50 GbE half-duplex instead of 25 GbE. You would need a different network card though (ConnectX-5, for example).

Pragmatically though, you could also aggregate (bond) multiple 25 GbE network card ports (with Mac Studio, you have up to 6 Thunderbolt buses, so more than enough to saturate a 100GbE connection).

Too bad Jeff Geerling returned his Mac Studios to Apple. Would be lovely to see how 5x faster RDMA impacts the performance.