The quick release locking mechanism on Capture and CapturePRO can withstand over 200lbs. of force. This is more than enough to hold any camera/lens/battery combination out there. You're probably asking yourself "are they serious?" to which we say yes, we're more serious than this extremely serious looking customer:
From a practical standpoint, the limitation you’ll face is the sturdiness of the strap, belt or substrate you choose to attach your Capture unit (and camera) to. On a backpack that has a lot of weight in the back, a sternum strap, and a waist strap, you’ll be able to comfortably put a lot of gear on it (i.e. a 70-200 lens, full-frame body, etc).
A professional camera belt can easily support a number of Capture units, each holding a body and a beefy lens. On the flip side, a thin belt that rides below the top of the hips isn’t going to hold as much weight.
We've got a whole article full of tips for using Capture with big-ass cameras, so you should read up on that if you're packin' heat.