Hello Nick,
4x + 20% would be hitting all the bases here 
seriously, my current problem is that, to update 24h of changed data on my ~61.7M files / ~25.51 TiB repository, restic backup is taking almost 24h, and so running the risk of overwhelming my backup window and starting to pile up. To be on the safe side, I need to reduce it by 50% – so ‘just’ a 2x improvement would be enough.
Wow, @ncw, as they say: signed, sealed, delivered! seriously, thank you very much for digging this up. And of course thanks @fd0 for bringing it up in the first place.
Examining the above and also the restic Design Document, I can see it’s pack size (and not blob size) which needs to be enlarged.
Very encouraging that @Pneumaticat reported back in the above thread saying that, just by changing its pack size, restic started “maxing out my [his] current connection to Google Drive”, looks just like the ticket here.
Unfortunately I can’t start testing this right now because the machine where I have enough memory to run restic with this repo is almost 24x7 already running restic backup in production during the week – and this weekend, I need to test and document the restic restore procedure. But next weekend I should be able to patch my restic tree here and try this out. As this is starting to get out-of-topic here, I’m moving the discussion to the topic you pointed.
Thanks again, Nick!
– Durval.