i'd like something that will handle a bit better than an 80's UJM.
An 80's UJM (while not the end all be all of beginner motorcycles) will probably be able to handle anything you can throw at it. Especially as a beginner. It's recommended that new riders begin on bikes under about 50hp. Alot of the recommended UJM's come in over that amount, but because of the nature of the power delivery, many experienced riders feel comfortable in recommending them to beginners.
It seems to me you are looking for ways to justify your wanting a faster bike. If you want one, go out and get one - no one here can stop you. Packrider
(Who is taller than you) Mentioned that he fits fine on the gs500, yet you pretty much ignored him and just went straight to the more powerful stuff again.
You also have a misconception that a bigger engine means better ergonomics. Quite often it doesn't. You need
to go to the bike dealerships and sit on some of the bikes you are interested in. Get a feel for them. If you find something that you feel you fit on, and want more advice, feel free to post back.