Adding the crossmemberframe to the back won´t do anything essential for strengthening the cars structure - it´s simply a bolt-in (mind: NOT glued in!) structure for fitment of spare wheel.
Imho most cracked windscreens source to inadequate fitting/erecting of the "old style hood", which is standard on all 4/4 and +4 Sports - and mind: all/most people writing about window cracks have exactly these models!
To start buttoning the hood on the screen and only THEN fixing the rear buttons is the way not to overstress the window(frame) with inadequate tension. Dismantling starting with the back is better as well. Even better is adding the hood swivels to the procedure (using them makes it a lot easier and safer for screen & fingernails....)
But all of this is just my own experience and technical understanding (plus the advice of MMC when picking up my car at the factory..)
It doesn´t matter how fast it becomes, but how it becomes fast. 2015 Roadster 3.7
2015 Roadster 3.7
