I have built two, a 22 and a 30, and have two stamps approved to build a 45 and a 9mm. For the 9mm and 45 I'm planning on using premade stainless cones. There are several companies selling them on eBay and other places.
I used coned freeze plugs with perforated square tubing as the spacers in my 30. It's 10" long so the extra length helps it be reasonably comparable to the average 8" commercial can. It's not a lightweight but on my Ruger American 300 Blackout it makes for a manageable package.
Can you please elaborate on how to fill out the form so you can rebuild a silencer? I thought it was pretty well established that once it was complete only an SOT could make repairs.