the Saiga 12 is now my go to gun,I too use it for 3 gun... I did the conversion from sportster style to AK-12ga myself, easy job especially if you have ak's already.
I found the birdshot/target rounds boring pretty quickly so I bought a Lee 1 oz slug mold and am casting and reloading my own 70cal slugs using the roll crimper......hootie hoo what a blast...found the right charge to cycle the gun and cut back on some of that awesome penetrating power, there is not much need for high brass slugs, even low power (enough to cycle the saiga) they are devastating
I prefer the Promag 12 round drum its not so heavy and bulky as the MD20rnd drum, but both feed flawlessly, I bought some 12 round banana style mags but they look & feel awkward so I cut them down to 8rnd and they now look more proportionate to the gun, I may just be used to the look of my AK's
stock NON adjustable sights then became a wee issue, was shooting a little low using iron sights, so I installed the red/green dot holograph, amazing accuracy with the slugs Im dancing milk jugs at about 100yds
I choose the Kvar folding stock because its rugged steel and folds to the left to leave the action free and with a small adjustment to the stocks catch, I made if so it closes with the 12rnd drum in place....
Rambo would be proud!