I've never heard of a S2 they did have a Q2 or SQ2. Mathews bow are draw specific so to change draw length you'll have to buy a new cam and I'm pretty sure that the cams aren't interchangeable so you'll have to buy the cam that's made for that bow. On your limb question if the bow has 60-70 lbs limbs set at 60 then you can just crank them down to 70. If they're 50-60 lbs then you'll need to buy new limbs.