Hi Colin,
My 1st gyro, a 'DC Gyro' designed by Emilio Cabesas & published in RCModeler in 97 or 98 is an excellent machine.

However i built my blades for it from medium soft balsa with no hard leading edges. It fluttered badly & crashed numerous times.
I had to scrap the blades & make new ones from firmer balsa with 1/4 sq spruce leading edges. The result was no more flutter.

Hope this helps.
Bob Gardner