Mel,
I have CFRD and JUST got a g-tube (a month ago), and I'm very happy with it.
Prior to the g-tube I was using Humalog and Lantus for treating the Diabetes.
Since I do my tube feeds while I'm sleeping. Endo added NPH to my routine because it's duration is 6-8 hours, covering the 8 hours of feeding. (taken 30 minutes before start) Insulin is adjusted depending on how much nutrition and b/s numbers, of course. (I happen to take 8 units). I continue to take my other insulins as I did before the g-tube.
As for enzymes, I take them just before the feeding, and again when I wake up (8-ish hours later). Ideally, if you wake during the night for any reason, it would benefit to take them then too, but, our dr doesn't want us to purposely wake to take them.
I hope that helps.
Edited to add:
My morning numbers are always on target now, compared to prior. So, I think all-in-all, it's been very beneficial.
Also, If you are thinking of getting one, I'd recommend during it while admitted (verses an out-patient), that way Endo is there to help monitor and adjust. In the beginning, my b/s numbers were very high, but they got it worked out, and I've had no problems since.