Actually, this topic has been discussed on this site several months ago, but don't know if the posts are still available.
In a nut shell, yup, these work. In fact, I think Destry is still using a set on his KX500. However, you can improve steering on you big green machine by simply pushing the forks up so a small portion protrudes above the top tripple clamps.
I run my forks 1/4 inch above the top of the tripple clamps for high speed desert races, and as much as 3/4 high for really, really tight technical enduro races in the trees. One thing to remember is that as you increase the fork height, you will transfer more weight to the front of the bike, and change the effective rake of the front steering assembly. The result could be headshake, which everyone knows can result in a quick (or slow, depending upon the extent of injury
) to the hospital.
If you are not running a steering dampener, I would not drop the forks more than 1/4 inch for any fast riding.
Experiment with the fork position, adjusting the forks height slowly, in small increments. Choose a section of trail that has high speed sections, as well as a little tight technical areas, and use this as your test section. Ride is a number of times to familiarize yourself with any obstacles, so you can focus on the bikes handling attributes as you make adjustments. The process will take you a couple of hours, but you will find that your corner speed will improve substancially.
Good luck
Rick
