[Sid Squid]

Start looking at bracing for the front of the frame, around the headstock, this is an area where useful differences can be made. Also add an 'X' brace between the front frame downtubes below the header pipes, and if possible a brace/plate where the upper frame tubes curve under the rear of the tank, if it can be done without making the tank or carbs difficult to fit that is. Bracing the rear is always a good thing, but unless you're considering putting a big wodge of power in it, the front is where the biggest improvements are to be had. Kawasaki knew the deficiencies their frames had, hence the sheet braces around the headstock - beef that up.

If you look at modern frames you'll notice the headstock is much lower down and the forks are shorter, that means the leverage, (particularly side to side), the front wheel has over the headstock is reduced, stiffer front end gives much better steering and less frame spring - put your effort into the front end.