Not really looking for a debate but I am going to have to disagree with you on a couple of things.
I wouldn't consider the eclipse to be on the beefier side. Admittedly I only own a couple of them but they are just middle of the road Envy's.
Also, the soft neutron (again I only have a few of them) are some of the more high speed stable Envy's I own.
Honestly I completely agree with you.
Some people seem to think that the eclipse is stable but I found it fairly neutral and workable and I also thought that with it getting dark so soon it's not a bad disc to have in the bag. I find the soft neutrons a little bit less high speed stable but they are plenty low speed stable they seem to hook up fairly nicely
I just find the softs to be a little bit different from the other envies and if his son is throwing with a little bit of off-axis torque it may not be the best choice. But again I completely agree with you I have no problems with my soft Neutron
Pretty much any premium Envy will work and a clean throw with an electron one is still plenty stable and straight