I recently passed the 100 flight milestone on each of these two planes. On the left is the Parkflyers International Su-35, plans available here, support thread for this plane is on the RC Powers website here. On the right is the RC Powers Su-27 V5, plans and support thread are available here. Both these planes are built from MPF grade B foam except for the KF airfoils which are made of paperless Dollar Tree foam (Adams Readi-board).
I downsized both these planes to have 27" wingspans which is about 10% smaller than what the designers originally made them to be. As I might have mentioned in previous posts in this thread, I think it is going to be important for designers and builders to keep an eye on how big they make their planes if most of us in North America at least are going to be building with MPF instead of Depron now that hobby grade Depron is essentially disappearing.
I put very little paint on either of these planes to save weight and also to see if over time the bare foam might break down over continued exposure to the UV rays of the sun. So far, so good.
I used 4mm carbon rod for the main wing spars in both planes, this is twice as heavy as 3mm carbon tube and I estimate at least twice as strong, but I think necessary to prevent losing energy to wing flex. If I had used 3mm carbon tube for the main wing spars, I might have saved a few grams, but I know I would be seeing wing flex. In both these planes, I added about 25 gr/0.9 oz in extra reinforcement and I don't really think I could have got away with any less otherwise critical areas like the back plate which takes a lot of torsional punishment from the elevons moving to maneuver the plane would have been twisting and flexing significantly. Also, without some bamboo skewers in the vertical stabilizers and elevons, I am sure these would be quite flexible, affecting how the plane handles and performs.
Given that I like my park jets of this wing span to be in the 21-22 oz (595 - 633 gr) range, it will be a real challenge to keep the build techniques very light as well as any paint jobs I want to do will have to be kept as light and/or minimal as possible, otherwise the planes will end up too heavy for my liking anyway and not only does top speed get affected, but also wing loading which then makes the plane less maneuverable and agile.
Other than the increased weight due to the need for increased reinforcement, I have no real complaints building score and fold planes entirely of MPF. It will just take continued ingenuity and adaptability to keep the builds as light and strong as possible.