I flew a SL3 in Wyoming once, It was great, had Parsons rotor blades and a Stability Augmentation System (SAS), the company also had a SL4, but the rotor blades were hard to come by. (It had hydraulics, no paddles)
I wish I could have flown it more.
The SL was a misnomer of sorts, really a "L" with the optional Lycoming TIVO-540-A2A. a 315 horsepower "Turbosupercharged" engine. I am not making up the word "Turbosupercharged". Great high altitude machine.