I have learned the hard way about Reynolds numbers and scaling airfoils. Fortunately it was a virtual crash and burn.
What I had done was create my full-size XFLR5 model using the PRANDTL-D airfoils, which I think are Horten-like in design. This did not work at all when dynamically scaled to 1/8th or even 1/5th scale.
But then I changed to a Hepperle MH46, because it had the same 12% thickness and was made for lower Reynolds numbers (besides low pitch moment). After a it of tweaking, all the models worked fine.
Since the MH46 was designed for the lower Reynolds numbers, my question is: Are there any problems with scaling an airfoil up in size to use at higher Reynolds numbers?