1 inch is plenty to fully blend into a sleek 1/2A design. Proportionally the same as a 2 inch spinner on a .40-50 size plane. The stresses from rpm on a 1 inch spinner won't be too high.
On a bushing engine a spinner might cause rapid wear. Especially if the plane does a lot of quick changes in direction.
I never could get an Ace spinner to stay on a TD, it would shake them off like an angry bull at a rodeo.