The first thing you need to do is make a mod for the missions you're working on. Do not worry, this is very easy and will not hurt at all.
Step 1: Create a mod folder. Simple as that. In your FS2 folder, create a new folder, and give it a good name. In that folder, create a "data" subfolder, and within that one, create a further subfolder called "missions" and one named "tables". The final layout should be:
FS2 directory
> yourmod
> data
>missions
>tables
2. Copy all the missions you have done so far into the mod's missions directory
3. Create a mod.ini. Within your mod's folder, create a text file called "mod.ini". Make sure that the file extension is .ini, not .ini.txt.
Copy the following text into it:
[launcher]
modname = YOUR MOD NAME HERE;
image255x112 = PLACE FOR COOL GRAPHICS FOR THE LAUNCHER;
infotext = AWESOME BUT SHORT DESCRIPTION;
website = WEBSITE FOR YOUR MOD;
forum = FORUM OR THREAD FOR YOUR MOD;
[multimod]
secondarylist = mediavps_2014;
Make sure to replace the ALL CAPS text there with appropriate things. Lines you do not wish to use can be deleted.
4. Get a VP file editor. Personally, I prefer
VPGUI, but there are differing opinions there.
5. Open the ships.tbl file that defines the ship you wish to modify. For ships from FS2 retail, that table can be found in root_fs2.vp. Extract the file to your harddrive, and open it in the text editor of your choice (notepad++ is the choice of the discerning FSO modder, but any will do).
Search for the entry where the ship you wish to modify is defined. Copy the entire entry into the clipboard (entries end when the next entry starts).
6. Create a new text file in your mods' data\tables directory. Name it "yourmod-shp.tbm".
7. Copy the following text into it:
#Ship Classes
#End
8. Copy the ship entry from step 5 in between the #Ship classes and #End lines.
9. Rename the ship entry to "<original ship name>#Cutscene". This will create a duplicate of the ship. Note that everything following the # sign in names as well as the # sign itself will only be visible in FRED.
10. Change whatever parameters you want to change, and save the file.
11. Open the Launcher, and select your mod as the active one.
12. Start the debug executable. This will check all your tables for correctness. If there are errors or warnings, try to correct them.
13. You're done! FRED away to your heart's content!