Looks like I found a sweet spot - got 81.87 MiB/s:
# uplink cp -p 8 -t 8 --parallelism-chunk-size 256M sj://akash-snapshots/rpc.nl/akashnet-2_2022-12-08T22:32:30.tar.zst /dev/null
download sj://akash-snapshots/rpc.nl/akashnet-2_2022-12-08T22:32:30.tar.zst to /dev/null
...
2.35 GiB / 1.51 TiB [>___________________________________________] 0.15% 78.92 MiB p/s
2.85 GiB / 1.51 TiB [>___________________________________________] 0.18% 81.87 MiB p/s
...
11.09 GiB / 1.51 TiB [>__________________________________________] 0.72% 81.57 MiB p/s
11.12 GiB / 1.51 TiB [>__________________________________________] 0.72% 81.29 MiB p/s
Useful link Hotrodding Decentralized Storage