Update 6/29/2022- I was able to do some testing. The mod worked quite well. I was able to get around 20 rounds in, that successfully ejected, before I had an unrelated issue with the barrel coming unglued. More testing will be done in the coming days.
Experimental and untested. This is intended to replace the rubber band with a spring. Assemble upper to lower receiver. Insert spring behind bolt and install plug into the lower receiver buffer tube threads.
Spring located here. https://www.menards.com/main/hardware/fasteners-connectors/specialty-fasteners/springs/midwest-fastener-reg-53-64-x-3-zinc-compression-spring-1-count/88033/p-1444440207146-c-9553.htm?tid=473015708422502303&ipos=1
AK trigger prototype. The discoverer needs to be beefed up if printed. It can be made from some kind of metal. The rod needs to be 2mm. A stainless rod is recommended. The rod needs to be bent to fit your specific application. It must go over the left side lower rail. It will travel forward and catch the lip of the bolt. There should be a small gap between the bolt and the lower rail on the left side. Mark your bolt at the notch opposite the auto sear notch. Transfer the mark to the receiver. Make the rod's tab this distance so the plate is forward when the tab is at the location of the mark. You are better off long than short as there is a bit of room for error. The return spring is a standard Gl0k trigger housing spring. Weight doesn't really matter. This is for prototyping and educational use only. Not for resale or production.