H-9 planes have fuel proofing on there fire walls, just because it has a cowl has nothing to do with wheather or not its had a coat of fuel proofer added.

now if you wanted to add a little extra there's nothing wrong with that.

after removing the engine mount,dip the mounting screws in some Vasoline and screw them into there locations, apply epoxy to the firewall and use a heat gun to warm the adhesive this will thing the glue to a nearly water like consistancy then brush it out to cover the wood after its dry pull the screws and reassemble simple as that.

this also works for the tank area,as a side note I like to nuke my epoxy, pop the tops off the epoxy bottles, so they can vent a bit, and place them in a micro wave on med. for about 5-10 seconds this will thin the 2 parts, allow to cool slightly and mix them the thinned mixture can be painted into the tank area,in a tight spot it can be poured into the tank area, and the fuse can be rolled so the glue can get into the nooks and crannies, this also works well for fuel proofing.

it also helps strengthen the joint between the firewall and fuse, use at least 30 min epoxy if you heat it since warming the glue speeds up hardening times