Got my friend's M72 Yugo RPK working as a three position FRT. It is working decently well. It can still choke up if you crank down super hard on the trigger, but it runs decent and doesn't require feathering.

Combined a standard FRT kit from SuperSafetyShop with a highly modified full auto safety selector and a full auto disconnector.

Waiting on a suppressor mounting muzzle device and a Wolff extra power recoil spring in addition to an ALG extra power hammer spring. The extra gas from the can plus the extra energy storage potential of the stronger springs should increase reliability even when pulling the trigger HARD, and increase reliability overall.

One big takeaway I've learned with FRT systems is that the user input via the trigger finger basically robs energy from the reciprocating system. Reliable function then requires MORE system energy than a lot of platforms were designed to function with originally.

I tried getting three position to work on some of my AKMs but was unable to.

https://streamable.com/znd72g