Stosh loves frisbee too but like Shade said I throw the frisbee along the ground and he chases it. If I do throw it in the air, I throw it at his head height so he doesn't have to leave the ground for it. Jumping at any age isn't good but can be especially harmful in dogs under 2 yrs old. The growth plates at the ends of the bones haven't finished growing yet and you don't want to damage them. By the way, I get Jawz Hyperflite discs for Stosh and he loves them!
Max is 98lbs, and 8 years old, hes obsessed with the frisbee, I time it right when he starts running to throw it so all he has to do is reach for it, all 4`s are on the ground, also use a kong Frisbee, a gal at class has 2 Ausies, they were playing with a cheap plastic frisbee that was broken, freak accident and one of them lost an eye from the broken frisbee