Hello! I noticed a few things, I either encountered same questions when I was building mine or I read/heard about them so I could be wrong:)
-Geissele trigger wont work with firing pin safety unless you take it off from the bolt carrier.
-If you are using the ctr stock, why get the commercial tube? Milspec diameter hk stock can be sourced.
-Are you building the tan 416 or the earlier black ones? If you are doing the tan version I highly suggest you to get the geissele DDC tube, as I did for mine.
-Source a geissele handguard if building tan version.
Lastly, check out this website for clones: https://www.clonerifles.com/theclones/hk-416d-cag