The Brass Head Nymph is inspired by Hans van Klinken’s Lead Head Nymph he uses to fish fast, deep water for Grayling.
Unlike van Klinken’s pattern which uses a lead split shot, this pattern uses a brass bead which, while not as heavy, is perfect for the shallower, slower waters in which this was designed to fish. To make it heavier I would simply substitute the brass bead with a stainless steel or tungsten bead.
This is the pattern that the heavier Sure Thing was based on.
Both are excellent Chub flies and will attract the attention of other river species.