I don't see how this would fix any of your problems unless you had a serious rail-to-rear trunnion height dimension problem.
"Landscaping" Steve is an idiot: the top cover does not retain your carrier inside of your receiver- the recoil spring does. That's why it locks into the rear trunnion. If it's skipping out of the receiver, you've got one shitty POS receiver. You've got a height difference between your rear trunnion and your rails, and odds are it's where the rear trunnion was mounted, or where your rails were spot welded that caused this geometrical problem.
This is one of those things that tacticoolers add because buying tons of shit for a rifle gives them pleasure because it has to be good 4.5 stars on Amazon means it's sweet. Buy an AR. One of Eugene Stoner's product definitions was "must accept as many paintball/airsoft accessories as possible." FACT.