This is old but I found it interesting to read. I have a couple tech things to add too.
First, I think someone tried to correct maichor earlier, in that the Q45 uprights are aluminum, not cast steel. I have a complete subframe from a '92 Q45 and they are made of aluminum.
Also, someone asked about the subframe/suspension weight. Mine is complete (vlsd R200) except for rotors, calipers and struts and weights exactly 250lbs. Granted it is much wider than the S30 track in stock form but it still seems about 100-120lbs heavier than the stock setups with an R200. How much to the hubs, mustache bar, diff mount, controlarms, axles/shafts weigh? shortnose r200 is 86lbs?
I'm going to try and take off about 50lbs (narrowing (10"?), removing harmonic weights, shortening front arms slightly, replacing cast steel arms with aluminum etc.) I will weigh what I cut out and unbolt from the car when I do it and post what I get.