It's worked well for me over the yrs. Taller works better I think tho if it had a bigger storage area it wouldn't be a problem. As I mentioned, I'm not a big guy and with the bag all the way back against the topcase, I have to be riding no-handed to be able to lean on it. One of the best features is the outside pockets for quick storing gps, sunglasses, etc. at stops. I've never once had anything stolen.
Mine is a
Nelson Rigg, specifically an obsolete CTB350. You can still find them
on ebay pretty cheap if you want to try something inexpensive. I also have the small round RiggPak case that attaches to the top of it for even more stuff.
IMHO as infrequently as it gets used, being non-waterproof really isn't a problem. I do spritz it with Camp Dry before a trip but it came with a cover that has yet to fail despite my best efforts of hurricane and tropical storm riding.