I just saw this thread for the first time.
1, From what I can see your frame is made of polystyrene. Is this correct? If so, it is fragile.
One method to get it stronger is to pass thin rods of fibre glass.
You can buy these from ebay for a low price and they can bend to different shapes.
I have used these on my quad copter, to provide some crash proof/protection.
If you check some of my threads, you will see my videos of my copter and just before take off, you can pause the video to see how I have used these rods.
During flight tests, these rods can save your air craft from major damage.
When developing air craft you have to expect plenty of crashes (this is normal) and during this time, you need to build some form of protection, otherwise you will constantly be building new aircraft (which is not ideal).
For added protection you can use Gaffa/Gorilla tape.
Using fibre glass rods and Gorilla tape can make your air craft very strong, for very little cost.
2, Also are you using the PXFMini or the full EB2?
3, And do you have any videos of the aircraft in the air?
4, Where have you positioned your motor(s)?
5, How many motors are you using?
6, And what size propeller?
7, Do you have any specific purpose for your aircraft, once it is built and flying reliably?