I did, one of them.
If index.html will be your first page all other should be in cms.
Option #2
Use two Joomla templates :
1) Very very basic (plan) for home page
2) GK template for others
on homepage publish only one article (or Custom HTML) where you put your HTML code inside. so people will see only this code (and maybe menu module) and all others site will be filled with "normal" content.
Now its your turn. GK forum is not a ostraining.com website.