Oldfart,
Get hold of a pair of top out springs from a set of 38mm kayaba forks (same as you have) and put them above the XR springs. This will reduce the spring rate by about 2 lbs/in. Doesn't sound much but makes a big difference.
Give teh springs about 5mm preload.
If you have the spare cash get some YSS PD valves or Race-Tech cartridge emulators.
Brent