Request Suggestions for Caching OPNSense Updates

[abalsam]

I have a home lab in which I study networking and pen testing.  Unfortunately, my ISP has a data cap which limits me to 1.2 TB/month.  I have set up a SQUID proxy to cache my windows/LINUX updates but it is unable to properly cache my OPNSense updates (the initial download completes but when subsequent OPNSense VMs try to download the same update from the cache, the files fail to download (update fails).

I have looked at maintaining a local update server via RSYNC, however, since every update (including betas) consists of hundreds of megs, keeping the local repo in sync will tax my data cap as well.  That is why I am looking at only caching the files I am actually using/need.

Since I am not finding luck using SQUID to cache and keeping a local repo in sync will not help my data cap, are there other methods/setups people have found to work?

Thanks