there is a specific product for this.
This product is a particular "gum" for protecting the composite from the fuel.
A friend of mine has already used it for a cafe race tank and it works fine, durable and liable.
The product is
(Sorry the site is available only in Italian)
I have seen side aluminium tank but never a side fiber tank.
The tanks made by my friend are all front tank, and the fitment is easy he normally glue,
with epoxy+hardner, some aluminium bracket to the tank but I’m not sure this would work for a side hanging tank!
Any suggestion or experience on how to made the attaching point would be appreciate.
Have a good week end you too.