Hi Ralph.
I used Oracover. Regarding the sticking part it isn't easy with the 3D printed parts. In summary, you can use the iron but the timing is important, just a quick pass.
I would suggest, if possible, always have a different material for the covering material to stick to. For instance, in the wing trailing edge I have balsa and I was at ease.
I plan to try the plane when the weather suits.
In the meantime I am thinking if I will start a new project, ESCALIBUR. Wing in foam and covered with balsa. Fuselage, 3D printed.
I have also completed an easy one, the LIDL foamy. I have tried it and it flies well.
I hope that all is good.
Keep in touch,
Filipe