for aligning the chain and its rear sprocket
use allways and only the so called "laser cat" as described here at my homepage.
rear wheel alignment tool
and forget the marks at the swing arm´s end - they NEVER are that exactly as wished.
they can only be used for a rough alignment of the rear wheel - never 4 more.
a light beam is allways straight where ever u turn screws - earth, moon , mars etc.