I didn't think you could change hitpoints serverside..if the carrier doesn't cause a crash I'm very surprised.
You aren't testing server-side. You're testing client side.
To test server side on a local machine:
Copy 1942 folder, name it "BF1942 2".
Put all mods in that levels folder.
Start dedicated server on "BF1942 2"
Join that game from your regular one. Bam, just like server side.
If you want to make them harder to kill.....you might have to go to the damage system, and changing lots of weapon data could be fairly time consuming.
Maybe if you made a new material for the landing craft...that might work. Are you familar with the damage system?