As an alternative, what about removing the 17T sprocket from the eight-speed Shimano CS-HG50-8I cassette (11-13-15-17-20-23-26-30) and adding a 42T sprocket to lower development to 1.8m?

Oneup Components 42-tooth Cog for Ten-Speed Cassettes - Reviewed - Pinkbike

Birdy light | Riese & Müller