I don't recall having to compress the stack to get the snap ring in? A little pressure is all I needed to fit it together. Pretty sure nothing goes between the piston and apply plate. First plate on top of apply plate should be friction plate. Need to make sure the pack has the proper clearance when loaded in housing with snap ring installed.
This is very important. You should also easily be able to spin the planetary sun gear without feeling the pack drag. Hope this helps others that read this as he has probably corrected this issue.