Since my pouch in 86, I've done tens of thousands of abdominal reps as part of my 3x weekly work-out. As the movements are controlled and not 'explosive', I believe they have significantly helped my overall physiology.
Keeping my core strong has undeniably helped my back (L4/5 discectomy), and in my completely unfounded opinion, has created a strong and stable 'girdle for my guts & pouch.
Crunches, the ab wheel, lots of planks, hanging leg raises done with correct form and in a proper progression, I think, are 'safe' ... but everyone needs to evaluate the various inputs ... be honest about their own capabilities and decide for themselves with their own surgeon's guidance.
What works for @Jaydog may or may not be good for others ... but if it works for him/her, I respect that ... but again, we should each decide individually.
@Jaydog - good luck with your second step & takedown!