i'm on my 5th ulysses and have mounted a strap-mount bag on each one. smallish and low is the way to go on a uly IMO. see link below. these are extremely well made...strap system simple and bomb-proof...bag stays put...holds lots of goodies...has factory rain cover. nothing against what you now have but something that size looks ungainly on a uly.
http://www.ebay.com/itm/Nelson-Rigg-...tV6NdA&vxp=mtr