Hi!
The only way to use duct tape or (Flite metal) is to cover the surface with 24-30 hour epoxy and 25 gram glass fiber weav or (not as good) polyester resin as his gives a hard surface and then filler.Filling dents is done with brown micro balloons and 24 hour epoxy.
But I would not recommend this metod for a small ,1,7m span fighter plane as the weight is going to be to high. A much better metod is to sacrifice perfect scale looks and just aim for good fly-ability and using Oracover and do as I showed with my DC-3. Wet sanding pieces of chrome Oracover on a glass surface ,sanding with 1200 wet sand paper. Plastic film (Oracover) is much lighter than duct tape (Flite metal).The only places I have used duct tape is on the engine cowlings as the surface is much too sadel shaped and on the side rudder where I have used Oratex (same as Solartex but a little better).