Hi Ryan,
My imaging rig is an 8" Meade LX200 ACF.
I mainly flick between f/10 and f/7, depending on targets.
I'm really happy with the scope and like you mentioned, I love a challenge.
On a side note, I really enjoy getting up close and personal with my targets. Having a longer focal length is one way of achieving this. I particularly enjoyed this aspect when I captured the black hole jet in M87.
Note: all images were taken at f/10, except Trifid and NGC 253. They were shot at circa f/7 using the same equipment. Mars was captured at circa f/20 (eyepiece projection).
Cheers, Evan