Thanks for all the help, but I would like to clarify some things.
From my understanding ordering the SD costume from RS and not modifying it at all reaches baseline 501st requirements (tier 1). Is this correct?
Secondly, I would like to create a concrete list of modifications I would have to carry out in order to reach PO level because I have contacted RSpropmasters asking them if they could do a few of the alterations as they construct it and they need to know what alterations need to be made before they can say yes or no to my request.
From what I have been told so far these modifications include:
change ammo-belt pouches from canvas to leather
change color of backpack from this to this
recommended (for durability), Change the hook and strapping method with straps and poppers.
Add a rear sight to DLT 19 and put the charging handle in the right place. (Or would it be easier to get an E-11 instead?)
Are all these alterations correct? Are there any ore that should be added in order to reach PO? Are any of them unnecessary?
Again, thanks for all the help.