That one screw works fine EXCEPT you should pre-drill it's pilot hole. There is really very little load on that screw. The engine thrust is basically straight ahead. Back in the '80s, I built a Seamaster 40 from a kit and the post for the engine was epoxied in. I consider the one-screw approach to be a real improvement. Mounting the throttle servo up in the engine pod with the groove for the wire is another great improvement. I built the ARF when it first came out and it has been improved in several small ways.

The nose cone needs better mounting. You should probably re-inforce it with fiberglass on the inside where the screws go. I lost mine in a spectacular cartwheel that was the result of trying to take off in water that was way too rough, and it took a YEAR to get a replacement. The one from Fiberglass Specialties is for the old kit version and won't fit the arf.

Good luck, flying off the water is great fun.