Hi GonzoRus, re: filleting failing - like Karsten mentions above it's probably because of the large fillet radius that you were trying to use there. In many areas it looks like you don't have enough space for a radius=5 arc to fit. The fillet will fail if you have that situation.

You would need to try a lower radius value for Fillet to have a chance there.

If you need more help or information about the areas where radius=5 does not fit, please post the 3DM model file with your curves in it so others can take a look at your actual model instead of only a screenshot.

Try using much smaller radius values like 0.1 , 0.2, 0.5, or 1.0 to see if those succeed ok or not, that's what I would be trying if you had posted the 3DM file. Or for a larger radius you might be able to make it work if you only select areas where there is space rather than trying to do the whole thing.

- Michael