The RPD links do come in two different styles. One style uses friction to hold the case against the L shaped rear of the link. The other style has a staytent formed in it that engages the extractor groove on the case to retain it. They are usually referred to as L style and U style based on their shape. I used the U style and squeezed each link just a little to reduce the inside diameter. It works great. Just go easy when you squeeze them or you will snap the spring steel.What modifications do the belt links did you need to do? I don't know what RPD "U" style links means? Do you mean "normal" RPD links, or are there different versions?The bolt, carrier, trunnion, barrel, gas system, etc. on these weapons are AK parts that have been modified to accommodate the RPD feed mechanism so I don’t really think it is incorrect to say it is based on an AK.I'm not sure would call that AK based..?I just worked on it in my spare time so it is hard to say exactly. I would guess maybe 30 or 40 hours in it spread out over many weeks. Working on custom builds is play time for me and I just wish I had more time to play.Looks incredible. How many hours of work went into the build?