Well yeah, you definitely don’t want just a heavy rear load. That’s basically the same as what I was saying about a bunch of weight on the rear rack handling badly. You basically went from the worst way to load the bike to slightly better. My first touring bike was actually an old Trek and I started out just loading the rear. It handled terribly. If it handles well now then rock on, but swap out that handlebar bag for some low rider front bags and I’d bet anything that it’ll handle better. Better yet, pack the bulk of your heavy things in front low rider bags and just your light weight bulky stuff in rear bags. Then it’ll probably handle almost the same as it does unloaded. I wouldn’t be surprised if you could coast down hills at speed with no hands(if your load is well balanced side-to-side).

https://www.bikeforums.net/touring/1...-panniers.html Check out this thread.

The rear wheel is the thing I’d be concerned about too. I’ve managed to bend an axle on a Bridgestone touring bike with an old freewheel hub. The first thing I’d do if the frame allows would be a set of modern 700c wheels. A modern rear hub at least.