Modifications to all my slow flyers including the GWS Beaver consists of adding a 1/4" hollow Alu. Tube throughout the model's wing span. I will add a second wing support strut for looks but, it really is fine since the Alu. spar holds the wing very well and securely. My GWS "SUPER" Piper has this strut and I am able to do snap rolls and multiple loops from straight and level flight (I modified my GWS Piper J3 Cub with the EPS=300C-CS).
On both the Beaver and Piper, I also added a more robust (Heavy Duty Landing) gear with double strut support. Minor safe guards to the foam at the wing attachment areas has been by adding basswood on the contact points.
That's the best part of your GWS products, the modeler can add significant safeguards and scale like appearence to the R/C model without affecting it's original flight design characteristics.
Way to GO GWS!!!!!!!!!!!!!!!!!!!!!!!!!!!!
p.s., here's a picture of my Piper and I, showing the ALu. Spar under the wing. As you may notice, the Piper took a similar loop but, the rubber bands held the battery in place and I flew the Piper with the Battery pack dangling from the wires! I had to make a smooth emergency landing. Wow!