Hey, just jumping in on this. I've recommended this before, but when looking for this kind of technical information look out of the hobby and go to the trade applications. Go where the industry goes for info and training. Also, be very leery of commercial/store websites as a source - the water treatment industry is full of snake oil and used car salesmen mainly using fear as their sales tool. Here's a link to the Canadian Water Quality Association that is more or less the "governing body" and training source of the trade.
http://www.cwqa.com/watertreatment.php
And a good article debunking misinformation
http://www.cwqa.com/water_treatment/misinformation.php
Can't remember all the little things I cringed at in this thread - but the R/O is *always* fed with softened water if available. Membranes don't like hardness or iron. Also check the specs on your unit before jacking around with the pressure or buying a feed pump - there are low pressure membranes out on the market.
Jim