this design is the best, fistly look at the pivot point and think where the part of the linkage that is attached to the shock is going to move. it isn't going to move your shock at the moment, you only need to move the frame/shock connection mount onto the downtube though and it should be good to go. then think about changing the looks slightly for mass/cult apeal

 could work but hella ugly...

 yeti

 yes, same swing arm looks as the yeti...