Thats about as high as you need to go with your SG with the F8's in there...As for the GSP, it sounds like he is still pretty small/young, so thats good for now, I went slow and took about 2 years to build up the SG in his tank to full marine before I moved him. As for being reef safe, I'm not going to say they are or arent, just going to say that I'm not having any problems, his other tank mate happens to be a Mandarin Dragonet and so far so good there too...but it all depends on the individual puffer. I doubt you would be safe putting any decorative shrimp in there though...lol. I dont have any in my tank but I do feed my GSP pieces of thawed shrimp (people food shrimp, not fish food) and he devours it, he doesnt mess with my hermits or any other of my clean up crew that I can tell, doesnt even seem to mess with the emerald crabs...yet, I'm still waiting for that day...haha.
Good luck
BM