Hi Papa
Not the most storage available on our B. I tend to wear waterproof jacket and over pants with zippered vents so I pack no separate rain gear. Saddlebags have thin bike cover rolled up small, few tools, tape ,tie wraps, tire plugs air pump, spray cleaner with cloth, heat out/freeze out jerseys, mesh jacket... Then I have a Torrent 40 liter waterproof bag for my clothes, boat shoes, toiletries. It straps on the rear seat. Like you, I can't fit everything in just the saddlebags. And it serves as a backrest. Maybe somebody will invent disposable clothes!
Small flashlight, helmet "T" to lock to bike, extra earplugs, small cloth to wipe off helmet shield and windshield pen, tire gauge in left cubby. Center cubby holds my GPS when parked for short time, sunglasses,
Happy trails!
WEG