I agree with everything you've said, but I don't agree with them not being good for a first time hot keeper.
Many people keep atrox as a first hot, and although they aren't built as heavily, they generally are far more nutty and tricker to hook.
What makes a gaboon bad for a first hot? If you cannot bring yourself to not underestimate these snakes, do you deserve to keep any hots at all? You should always over estimate regardless of whether the snake shows defensive signals or not.
My two gabs were my first snakes, forget about venomous snakes. I didn't keep non venomous at all. But I had experience dealing with large gabs, puff adders etc.
A friend of mine has the perfect hook for large Bitis. It is almost shovel like, the hook is about 7 inches wide, and is perfect to take big Gaboons out on and they sit perfectly on it.
Many people do tail Gaboons, however I'm with you. I personally would not do it at all, they are far too 'athletic' when it comes to striking.
I will try to get a picture of the hook my friend has, it's really useful.
Have you come across any of the 'dwarf' gabs? A few of my friends have adult Gaboons that are 6-7 years old and are only 3 foot.