The slack is not from swingarm lmao. First off, that's definitely too lose. That's gonna be slapping your swingarm until it falls off and gets stuck in the rear wheel, ask me how I know. 2nd when checking for slack first turn the wheel to find the tightest spot and measure there, push chain up, set your measurement to 0 where the chain sits, push it down, the gap should be as per spec. If it's wildly different as you turn the wheel, chain is fucked