See
https://www.takahashiamerica.com/mor...system-charts/
Specifically
https://static.shoplightspeed.com/sh...art-fs-60q.pdf
They don’t make it easy for you and perhaps a Takahashi user can recommend a simpler solution. For my TV-60 I remove the diagonal and replace with 1.25” T-adapter - camera T-ring - camera for prime focus. Perhaps you could do the same.