Sure, CG would be ideal/best, but I think there's a lot of leeway here. For convenience, I put most all my lugs in one of the fin fillets. Works fine for all my low-power rockets.
Quest's Viper (educational pack) kit has the lug molded into the plastic fin unit. Way below the CG, just like my own fillet lugs, but it's proven to be no problem in that location.
(BTW, I'm a newbie to this forum, and just getting back into the hobby after 25+ years away. It's great to now have a kid of my own so I can play with this stuf again!)f