Hi Terrier,
I am not convinced about that as its there to make a seal and stop paint rubbing so I need to leave it on. However I have now found the answer after I took the door skin off again
I wont deal with the handle replacement as that's been shown many times before. This should help folks who have a loose barrel because its not been seated properly.
The trick is to first make sure you have the steel ring locking the mousetrap tension bar in place. The second most important thing are the two catch lugs which MUST and I repeat MUST be correctly seated in the door skin handle recess to allow the barrel to seat at the correct depth. This ensures you can lock the barrel in place with the steel ring.
Oh and one other thing... make sure you have the handle pulled open when you are unscrewing the adjuster ring, it keeps it in the tensioned position so the steel lock ring can keep it in place once you remove the whole latch mechanism
Picture 1 shows the correct attitude of the mousetrap door lever tensioner after unlocking the barrel both after removal and prior to replacement back in the door.
Picture 2 and 3 shows the critical plastic locating lugs which must seat correctly in the door skin. It actually takes quite a lot of fiddling to get this right but persevere... it took about 10 mins to get this right.
Picture 4 shows how the steel ring should look when removing and replacing the catch mechanism. Yellow arrows are the barrel locating lugs. Green arrows are the catch plates on the steel ring.
I reckon 10 anticlockwise turns of the drive screw from locked barrel to unlocked barrel and obviously 10 clockwise screws to release the mousetrap and tension the handle again. When you screw the adjuster screw back in you should hear a clunk as the steel locking ring allows the mousetrap to retension the handle. Obviously make sure you have the pigtail wire from the door release in the handle as well.
I reckon it took me 8 times of door skin removal and replace to work this out
I hope this helps any of you with rattling rear door barrels.