I also have not used any of the thicker FB but I have had a large amount of experience in using the thinner FB, (3mm), and this was in scaling down FT designs and building at full scale in the thinner FB. There are significant differences when you vary the thickness of the foam centre layer.
The largest issue you may confront is that the thicker foam will make the FB more flexible as the foam itself adds a layer of flexibility or compressability to the material. When scaling down, to the thinner FB, the result was actually a stiffer and less resilient material.
The thinner FB also weighed more per unit volume and so increased thickness FB will have less weight per unit of used volume.
If you find your builds a little flexible I would recommend the use of a few FB stringers along the inside of the fuselage to reduce the tail boom flex, (if encountered).
For wings you will almost definitely require some form of rigid spar structure if you are to avoid a wing that is too flexible and could even appear to slightly flap in flight. Without a rigid spar structure the wings could even flex/twist in flight and the plane could become almost uncontrollable with issues such as control surface reversal becoming a problem as the flight speed increases.
Laminating the FB will improve the rigidity but the large amount of flexibilty of the foam will remain and you could quickly find that the weight is increasing faster than the strength!
Just a few things to ponder!
Have fun!