OK, I finally feel the need to respond. As an avid motorcyclist at one point, I would average over 10,000 miles a year on my '91 Honda VFR750F. I used it to commute, "tear up" the back roads/canyons, ride two up,tour two-up, and rode across the country. So, I may not have as much experience as some, but I've put some miles on. My VFR had little to no underseat storage, and it was a sport tourer. Under seat storage is the domain of the scooter. So, I, like many other folks like me, used a tank bag. It has got to be the handiest thing ever. I also had cargo net on the back seat, but that is a bit dorky I know. I think a simple tank bag would take care of a lot of your problems. Groceries though, need saddle bags. Welcome to motorcycling.