Has anyone had success mixing and matching cassette sprockets for custom ratios?
As far as I’m aware there are no 10 teeth sprockets for normal Shimano hyperglide freehub bodies because the freehub diameter is just too large. That’s why SRAM created the XD Driver standard and Shimano created the Micro Spline standard. 

Can’t you install a larger chainring and use a 11–30 cassette?