You can't chop the length off. It has a fixed focal length.
Piggy-back it to your scope and use it as a finder or as a secondary scope for someone else to look through whilst you are viewing. They will see what you see (to a limit).
I am going to do the same with my kids. I am going to mount their scopes on mine so we can all look at the same thing at the same time. Also gives their small scopes a more solid mounting!
p.s. Also good for visitors - keeps their grubby eyes off my eyepiece.
