the hanger 9 calls for a ,40 to .58 2 stroke,,

I want to use my older sk supertiger 61 to fly it..it will employ retacts and mfg.states flying weight of 6 to 7 pounds..will I be overpowering it to an exteme..???the article in model plane shows a 4 stroke 70..I would rather not have to purchase four stroke..one last thought I do have a unsed new older fs 9o..was going to sell it but it might work too..help