Your posted link is one of the key sites where I started thinking about c-41 home brew. Then I read a collection of old British Journal of Photography annuals, and trolled the rec.photo.darkroom archives.
Then Maxwell was nice and sent me a collection of his recipes.
My current C-41 formula is called Flexicolor Clone in past discussions on this site.
I have DIY'ed RA-4 when I was processing in tubes.
When I moved to a roller processor it oxidiazed too easily to work in the roller. I switched to Kodak RA-RT, and have been very satisfied with that product.
I do still mix wierdo colour print formula from scratch occasionally to do things like EP/2 prints, and reversal experiments.