I'm considering buying my first seatbag and Revelate seems to meet most of my needs. But I have a question to Terrapin owners: is it possible to throw in a larger (longer) drybag?

I can make one myself if needed. I was just curious if I could pack more than 14 liters into this bag with a custom drybag. Judging by capabilities of the harness - how far can I take it with weight? What do you think?