My experience, Stars and Stripes puffer and a wolf eel in a 55G, my early SW days and I did EVERYTHING wrong back then. I used to feed them both 6 live goldfish each every day. I was just doing what my LFS was telling me at the time. So they were pretty fat and happy. I had them both for over 5 years. Towards the end they used to get into some nasty fights. The wolf eel would come up and bite onto the belly of the puffer then wrap around the fish, and the puffer would blow up and fill about 1/3 of the entire tank when it did. Puffer had some nasty scars from those fights but it still made it. I ended up taking all my predators back to the LFS when I decided to go into the reef side.
Not saying a dogface and a snowflake would act the same, or if they did it may be more than a year, mine was about 3-4 years in the same tank when they started getting really aggressive. Just sharing my experience with a puffer and an eel in the same size tank.