The roller guard is a 20+ year old concept -- Some Martin and Jennings bows had them in the early 80's. The Mathews bows have the limbs at the swept back angle and limited limb deflection, thus the rollers will not pose any significant problems. The Martin version (in 80 or 81) could be adjusted as to position to give a 5# weight adjustment. The concept never really caught on.

The Q2 cannot be retrofitted with those string bumpers, as it requires an additional hole in the end of the limbs. You can probably get a multitude of other "add-on" string stoppers from other companies, those have been around a while too, but are not very popular (mainly because they are ugly and string whiskers work just fine).

BTW, I am a mechanical engineer -- since you asked.