Previously there have been questions asked about whether it was possible to stack perks with similar effects - for example, a Helmet and Gauntlets which both had Serpent's Tail (Grenade kills give more Super energy). I don't have the whole answer, but may have one piece of the puzzle. Hard data: Stacking two of the same perk with armor pieces does not seem to work, by my experimentation and others'. The Helmet and Gauntlets example above, for instance, would not give doubled bonus Super energy for Grenade kills. Thus, one of those perks is effectively useless (and an alternate armor piece should be used). However: More hard data: Stacking related perks using both armor pieces and a weapon does seem to work, again by limited experimentation. For example, use a Gauntlet set which improves reload for Hand Cannons, and use a Hand Cannon which offers a reloading-speed perk. Utilize both perks and you should see a noticeable improvement from one to both (you can make weapons reload with amazing speed, comparable to Defender > Force Barrier/War Machine. It is relatively rare for weapon and armor perks to coincide; for example, I've never seen a weapon which gives bonus Super energy for any kind of non-weapon kills, so I don't think stacking Serpent's Tail or Serpent's Mouth (for example) will be possible using the method above. However, super-fast reload is a pretty worthwhile benefit. Also, weapons like Lord High Fixer can give perks like bonus Grenade cooldown for kills with the gun, so you can easily stack cooldown benefits such that your abilities feed each other. I hope this helps the community, and invite others to post similar research results here to firm up conclusions about the game's mechanics. I didn't see any other topics specifically discussing this aspect of mechanics, please pardon me if I missed them (and link to them here, if you'd kindly). Thanks all and good hunting.