I don't have any of the typical 12v RV incandescent fixtures
We have recessed thin line 12v florescent fixtures
Actually did have
I cut the wires to the ballast, and installed led strip lighting from a five meter roll bought from Amazon
I did this to six fixtures...works great so far
3 strips in a 2 tube 30w fixture now uses 15w
2 strips same size fixture now uses 10w
2 strips in the smaller 18w fixture ( 2 *9w tubes) now uses 7 watts
A very nice power reduction/savings
And I no longer have to buy expensive replacement tubes