You'll just have to come to terms with the fact that you won't use most of the stored guns ever again and sell them. That or use the Claptrap storage to spread them out across different characters.
Got another Bee last night. \o/
Also beat Terramorphous a bunch of times, he drops nothing but crap on single player. The end game really isn't well thought out, my bank is totally full and I have only 5 spaces in my inventory for items. Everything else, I want to keep. I really don't know why they limited the inventory like this.
All the eurogamers who actually play with each other on xbl rather than just post pseudointellectual pc handwringing bollocks on the forums, love the shit out of biggy.