Michael, thanks a lot for all this so precious information amount! It is immensely helpful (I never thought, for example, that someone can do boolean operations with curves -I took for granted that such operations could be done only with solids-). I will try all the methods you mentioned! : - )))

Marco, by asking about a 'key' element in achieving nicely flowing surfaces I just wanted to learn if constructing in a way that does not have the 'zebra' precision could produce problems in 3D printing. I still do wonder why a fully solid object could have shape consistency problems in 3D printing. It seems that it will be necessary to experiment a lot with such printings for having concrete conclusions. I had never made a print to this day but it is time to do some... : - )