The SLC is rough, but that's expected. Trying to think of a way to describe it I can say that my GP friends were excited to ride it the first time of the day, and after the third they absolutely hated it. IMO it is a little smoother in the front than the back, but defensive riding is necessary.
As for the boomerang it was a similar situation, but I even enjoyed the first ride. Position is just preference on this ride.
Twister II hurts. My friend and I tried to ride with our hands up but it just wasn't possible at points to suffer the banging. The worst is how the restraint punishes your IT band on your thigh so watch out. I recommend the front, it just gets worse as you move back in the train.
As for the other coasters, sidewinder is a lot of fun that rarely has a wait. It does have the most airtime of any ride in the park, but for some reason during the loop can be a bit rough. Half-pipe will attempt to separate you from your man parts, but is fun.