I'll have to go through the appropriate channels to make sure it's safe to share numbers on average object size, but I can tell you that with the resumable upload feature you should be able to successfully upload an arbitrarily sized object, provided you're willing to pay us to store it. You can have a look at the documentation for resumable uploads here
. If you want to test it out, you should use a recent version of the gsutil tool and we'll automatically use a resumable upload -- there's documentation on that here
If your connection can truly handle a 10 megabit sustained upload, a 20 GB file should upload in less than five hours. That seems entirely reasonable to me. If you'd like to store it with us, I recommend you just give it a try, and share your results with the forum here.
If you really want to know how big our average object is, let me know -- I would be surprised if we're comfortable sharing that information, but if it's important to you I'm willing to ask.
All the best,
Google Cloud Storage Team