Its quite easy to do:-
1. Download the Design.
2. In the designer, select design. Give it a name Blah_Blah_of_Blah. Save as Template.
3. Find the design name Blah_Blah_of_Blah.
4. Add this to any ShipClass file under the size of the hull you want to move it too.
5. Start a game with cheat enabled.
6. Use unlock command.
7. Goto designer, find your Blah_Blah_of_Blah design from the ShipClass.xml (I usualy give the ship a name of "NeedChange_Blah_Blah_of_Blah" in the xml so its easy to identify), listed with its full loadouts in the build/edit que because you used unlock.
8. Select it to edit with the designer. Remove the Loadout(all ship components). Re Save as Template with a new name Blah_Blah_of_Blah_New.
9. Find this newly saved Template.
10. Replace Blah_Blah_of_Blah in the ShipClass file with Blah_Blah_of_Blah_New.