Default Depreciation Method When creating a New Object/Asset

I am pretty new to IFS, still getting a full understanding of all the connections within it.  My question is, our company is going from SL HY dep to SL BP depreciation.  So, obviously, when creating a new object/fixed asset, it defaults to SL HY depreciation method. 

Where is the proper place for me to update this default method to SL BP when a new object is being created, is it under the object group > Dep Method and Books?  Or is there a spot under Basic Data Fixed Assets where I can just check a box (which my coworker thinks but we couldn't locate it)? 

If I change the dep method to SL BP under the object group does this affect all of the previous SL HY depreciation objects once I switch the method?  Or does this just change the def dep method moving forward on any new objects being created?  As I said I am pretty green with IFS, last thing I want to do is make a change and blow the whole system up lol.  Any help or direction would be greatly appreciated, thanks!!