That's fair. CORS is a bitch.
For full transparency, the proxy is hosted on Zeit's `now` service and I don't even have access to logs so accidental leaks should be pretty safe.
If this is really being just run as a proxy setup, the jsonbrowse-proxy might not need the isomorphic-fetch lib, in which case you can just use the embedded node-fetch instead, which has max response size and timeout options available.