KRG quit making the conversion backbone in 2015'ish maybe 2014. I have one in my TRG-22, I got mine in 2014. Very occasionally you see one come up for sale. Now I run ARC mags with Area 419 extensions. I can load 12-14 rounds of 6.5 Sweedmoor/Addiction. When I got it I used AI or Alpha 10 round mags for 6.5x47. I couldn't get the 6.5x47s to feed reliably from the Sako mags, hence the reason I made the switch.
How many rounds can you get into your custom mag? What spring did you use to have enough strength after you joined them? You must be very adept at welding and put a lot of time into blending.