Why don’t you use spray foam to insulate the entire attic?
Although spray foam is a great product it is also more expensive then blown cellulose or fiberglass. Space is not as limited as in a wall and there for we can install a lot of a lower r-value and still end up with high R-Values. To get the best of both products a thin layer of spray foam helps air seal the attic deck, deters moisture from entering the attic and topping that layer of spray up with blown cellulose makes a hybrid approach of foam and cellulose more cost effective.