If anyone shoots with a rear bag, the xlr magnesium cargo butt stock that comes in the 28oz weight total, is virtually unusable. Has no bag riding abilities. You have to charge to a different but stock, and with the folder you're at 40oz, which is still acceptable and cheaper than the carbon version. I do not own a mpa chassis, but do have a Christensen MPR and krg bravo. I really like the MPR but wish it lighter.