looks nice ...
for foam, I just went through old packing boxes and found some pliable, but firm open cell foam that was older, but didn't seem to deteriorate at all.
the hardest part (for me) was getting all those blades inserted and hoping "the plinth" would not break or crack ... seems like you did fine.
.... I like to mark 'the plinth" and the mag with a marker in the same spot when separating so to get correct (original) orientation when reassembling.
OH, and don't forget to blow out (with compressed air) the gap , sure some foam dust got in there ... can see in your pic.