Stuff moving around on the bars can be distracting. Instead of jug on your bars, you might consider carrying a few 1 quart oil bottles filled with fuel in a back back or fanny pack, and then dumping them in to the tank as soon as you have gone 20 miles or so.
I've always wondered if the reservoir on the 89-94 could be used to hold extra fuel. I have a '94 and considered putting one on the other side of the bike. If you want to see a photo, go to the online parts catalog at bikebandit or somewhere and look under "radiator". I bet you could use some hose clamps to fasten that to a 97 - up KDX rear subframe. They go for about $32
They show up on ***bay all the time, new ones too. I've used one on my KDX as well as other older bikes, never had a problem on the cross bar. I always dump it in as soon as there is room in the fuel tank.