Seems like you may be over doing it with the down rigger if you're fishing 25'. You could achieve the same with a 3-way swivel and 3-5 oz. on a drop...then experiment with leader length till you get dialed in on the fish. Try that out for size. The options are abundant to play with. Good luck man.
We use our downriggers in 5-10 FOW for spring browns and coho to set light spoons just down 5' below the surface.
This way we only fight the fish.
Super control.
If you already have the riggers they work far better than most other presentations.
But yes, if you don't have the riggers, drop weights are a simple and inexpensive alternative to get things down.