Oh yes, this is one of the reasons why there is auto-aligning in this asset. You can download the playable demo from the store page and test this. The demo rifle has rails and there is also a demo attachment with rails (DemoCantedRail). You can pile as many of them as you want on top of each other (until they collide with some other part of the gun, because there is collision detection too). And if you place gun sights anywhere, they will still automatically align when aiming.