Tail spring mount

Hi all...
I?m working on 10-18, fitting the U00018 tail spring mount.
Page 10-18

It calls for shims as needed..my question is, what?s my goal? Am I trying to get this mount as snug as possible between the two bulkheads while still having everything line up and ?plumb? for lack of a better term?

Best practice is to not force parts out of their natural / relaxed position by pulling them into position with fasteners.
That doesn't mean you need to add a .003" shim to account for the last little bit of gap. Just use scrap aluminum material in the common thicknesses that are available to minimize the gap. Closing up the last little bit by torquing the bolt is fine.

Thanks. I installed 2 shims and have no gap...I?m thinking this is where I need to be but want some feedback.