cros chrome-sdk --board=<foo> knows what version of the SDK to download. I believe this information comes from a last-known-good builder (or maybe just from the last successful Chrome PFQ uprev).

Either way, it would be nice if the cros tool printed out a clickable link to an unsigned test image:

https://storage.cloud.google.com/chromeos-releases/canary-channel/caroline/11009.0.0/ChromeOS-test-R70-11009.0.0-caroline.tar.xz

Ideally this would match what xbuddy://remote/caroline/R70-11009.0.0 uses.

Bonus points if it only suggests this when your test image is more than 10 days old.