> ¿looks that the final solid is more wide than the original profile.?
Yes that will happen if you set the Twist option to 'Flat' on a profile and rail combination you've drawn there, and if you've set a Flat direction at some random angle you will get unpredictable results for that combination. If you leave the Twist option to 'Freeform' you will get the consistent shape of the profile along the rail.
Why do you want to use the 'Flat' option for this, what is it you are trying to achieve? the Twist 'Flat' option also means force direction, so when you choose a direction the twisting of that profile will be forced in that direction.
Here is a short video showing what Michael has explained above about what "Set flat direction" is used for.
Say I want to model a simple spring at a certain angle, you'll see a simple helix and a square profile, the helix is at 45° to the 'Z' axis, in the previous versions of MoI you had to have the axis of the helix the same direction as the 'Z' axis, apply the sweep with Twist=Flat then rotate the model 45°.
