Hi Dan,
very welcome to the Sidewinder Addicts Club!!!
As you understood, I did not built myself the machine. The builder, with whom I got in touch, spent a mere 4 years to complete the project. He is retired, count abt 1000 h per year, the machine ate him something in the 4000 h range, to give you an idea. Since he sold the AC (2001), he built eight (E-I-G-H-T, four plus four, you did not misread!!!) other machines. The sidewinder was his first and most complicated machine, he told me.
As you said, you will learn a lot, but it will take you a hell of a time. Some parts can be tough to handle with, for instance the heat treatment of the main undercarriage, and you will need support of the local (!!!! read: the 500 miles around!!!!) other owners.
If you really want to fly a Sidewinder, you'd better source a nice machine, air proven, with its own born temper or features.
You will save a lot of time, and due to less and less industrial activity, a lot of money. Local shops to machine or manufacture specific items are becoming seldom, they can't afford to bother with one shot projects unless it is very well paid.
Keep us posted, a copy of the doc would suit me very well, pass me a PM please.
Tailwinds for your Amphibian,
Bertrand