I realize there is a place to enter the information in PACKING/OTHER for shipping dims but this is easily missed when adding the fastener. If it were in inventory it could automatically account for it upon selection.
This is a common way this is handled: It looks like you're already doing most of the steps but there might be some additional information.
Would you provide more information?
Is the end goal to indicate how many inches/millimeters to the outside dimension of the crate when a particular fastener is used?
Example: Look at the Collar field in Designs>>Other.
Actually now that I have thought about this a little more I realize that just having a thickness would not work as if you have more than one (say link lock) on the same plane it would keep increasing the thickness.
I think now just having the ability in the Design/Packing/Other list to enter the increase in dims is good but it might be good to have some kind of reminder or something to make sure that I don't miss entering an outside dim increase. Might be my age...but I forget...