I’m in the same boat for my 21Gen4. I’m flipping and flopping on whether to go 45acp or step up to the 10mm and Comp it. Both the 45 and the 10mm Compensated setups will require different recoil springs and barrels with the Exception of also having to purchase new magazines for 10mm. My plan was to hopefully make a deal with Irunguns and purchase some stuff from them and have them add the components to the order thru them or have my Shipment shipped to them Via GlockStore or what have you and pay their regular fee. Let me know if you go thru with it and I’ll do the same if I do and let you know how it went.