A couple of basic ship building issues.

1 - Is there any easy way to change the ship class?  I often have ships that I would like to scale up or down with minor changes and don't want to have to start from scratch to rebuild them everytime.  Or I find a good ship in the Workshop, but it is the wrong class.

2 - So many Sci-fi series feature small fighters and big carriers/battleships with very little in between.  I would like to use multiple fighters/fighter flights and fighter groups to fill these gaps.  Problem is I can't seem to successfully copy the fighters as a part, which I can then paste multiples of to form my Small and Medium "ships".  Something always seems to go wrong in grouping the single fighter design together and saving it as a part.  And sometimes the designer claims a part is "too heavy" to place.  Any tips on how to do this?