Doing it as an AP or bridged mode.. is CLEANER.. but not necessarily necessary.
Doing it the way you are doing.. COULD potentially run into some issues, say with games, etc... as you are going through TWO routers.. therefore doing NAT twice.. two firewalls, etc.
As long as everything works, you dont HAVE to change it... though i personally WOULD turn off the wireless on the CGN2 then.. just eliminate any possible extra wireless interfearance.