Scott,
An OAG would not be a good fit/ solution on the RedCat 51.
As an f5 with only 250mm focal length it, in itself would make a good guide telescope.
I assume you want to image with it. What camera/ mount do you have?
A small finder/guider attached to the RedCat would be a better solution.
Something like this:
https://astronomy-imaging-camera.com...inguider-scope