Hi all: just being reading this thread: one of my 'pet' interests. Sorry, but tripe is not high in protein at all: quite the opposite. But you are right that it is high in fat. It also lacks a lot of vital nutrients such as calcium which is important for growing bones etc.
Minced whole chicken, minced meat, chicken wings, a little bit of tripe (dogs love it cos it stinks!) and lots of raw, minced veg. A dash of SA37 to make sure they are getting all the minerals and vitamins (stops me worrying lol)is the way I have more or less gone over to during the past year, having fed Purina Propla