Hi
the limiting factor is the standard shocks, as long as your springs are flexible (and that is equally important), adding length to the shocks will improve the droop of the axles significantly and help keep your wheels on the ground so maintaining traction. The standard shocks have less than 7" of travel whereas the replacements we have will give nearly 11" but are still short enough not to bind under compression. The extended shackles will help with this as they allow more movement at the end of the spring when the suspension is under extension. Also removing the panhard rod and anti roll bar at the front will make a big difference although this is not recommended by everyone due to insurance issues but is a mod all my fourtraks have had over the years along with cutting off the brackets so that it doesn't cause MOT issues(if it isn't fitted it isn't tested). There are pics in the gallery of my F70 with this set up posted around 2 years ago in Feb 2008 and I am still running the same set basic up now although I have added a front prop spacer after dislocating and stripping a couple and also added extended brake lines to compensate for the added travel. There are a couple of clips of the car on You Tube search Fourtrak ouch 2 to see it.
Best regards
Dave
www.bloodredoffroad.com