Great software. One small thing: in the preview area, when two characters overlap, it generates a white spot on the overlap. This does not happen in the editing area. It would be preferable to not have this happen (I create handwritten fonts that have lots of overlap), though there may be a reason for this I don’t understand.
If that happens, it is a sign that the path direction of on of the glyphs in not right. Run the “Layer menu > Correct Path direction” on both letters.