many restricted subforums: how to optimize

[Democritus]

I need to use about 20 little restricted subforums like it:

-public area
-subforum1 (restricted to user 1,2,3)
-subforum2 (restricted to user 4,5,6)
-...
-subforum20(restricted to user 70,71,72)

My problems are:
-Witch mod/style should I use to hide restricted subforums to user without access? n(so that user70 only see -public area and -subforum20)

-should I make group for each subforum or is there a simpler way?

Thanks