Dry-hopping

So I am going to dry hop an imperial pale ale. This is the first time I have dry hopped. I am using Cascade pellets aau 5.9%. 2 questions: Is 1 oz. of hops for 5 gallons sufficient or should we get ballsy and use 2 oz? Has anyone ever done multiple dry hopping say 2 to 3 times (at 1-2 oz. increments) over a 15-21 day period? I am pretty sure this topic has been covered yet I cannot find any when doing a search. Thanks.

Depends on how hoppy uou like it. 2oz isn't overklill IMO.
Lots of people do a staged dryhop to add layers of hoppiness, the key is to remove any doses after about 7-10days to avoid getting a grassy flavor.