Michael, i would like to thank you for your deep reply!!!

> In the case that you're trying to achieve, you will not have that type of structure,
> there will be just one general surface and it won't be represented by an analytic sub-class.

Now i understand :)

> ...you've got 2 filleted results there, neither of which is ill formed, there isn't really any reason to consider
> the one with multiple segments to be worse than the other one.

Ok....maybe for me it's only for aesthetic reasons.

> But the things you are talking about trying to eliminate here are not "seams", they're just regular edges.

Thank's for the clarification. It was necessary!

> But just because there are some cases here and there where it could help with avoiding fillet problem
> does not automatically mean that you should put a ton of effort
> into removing as many edges as possible on every single operation.

I feel relieved to know that it's not necessary to put a lot of effort in order to remove as many surface edges as possible!

Now, some minutes ago, i made a little test involving 2 solids generated starting from
a traditional joined curve, composed by 2 straight lines and an arc,
and the other one obtained from the first curve, on which i applyed the Max's script transforming it into a single curve.

Well....the result surprised me 'cause on the classic solid the "shell" command
didn't work.

In the attached .png i tried to recap all the steps of the test.

If you want to spent again some minute to clarify this behavior, i'll thank you.

Nice night,

Marco.