Hello Draggy,

With EPO foam any of the methods you have most likly seen will work fine for durability. If it's about hard landings, dings, and hanger rash type durability, you can use carbon fiber or balsa in the corners or in areas where you know you will have the greatest chance of impacts like the wing tips, leading edges, the tips of tail, (elevator, rudder), and the belly if you don't have landing gear.
Just keep in mind that all these things add weight to your foamy, which works against the beauty of foam planes, which was most likly designed to be inexpensive, quick, and easy to get into the air, and not to be a kit that you have to put a lot of work and time into. Another thing to consider is that you did purchase an EPO foam plane and EPO foam is considered pretty resiliant.

Morris, Ductedfans.com