after checking other forums and talking with Rob from Nitrohouse here is what I have been told. The spiders are for high grip surfaces, mostly European tracks. They have less diff action then standard diffs therfore you need to use lower wt.diff fluid. With extra gears they have more natural friction and when used in the center will drive the rear harder. This make sense because the higher the diff fluid in the center the more you drive the the rear. You need to use about half the diff wt i.e. if you usually use 5k fluid standard with spiders use 2-3K. With a center spider diff I am thinking the correct set-up maybe 3kF 2kc 2kR!!