Hey Buddyboy,
I just got the RS-80, its awesome. Definitely worth the $.
To answer your questions:
The collection cup needs ZERO (yes zero) more room to remove. Theres a locking ring that twists off and you don't have to move it up at all. You can check
HERE and read under the "Got Skimmate" section.
I emailed Euro-Reef about the water level when I was thinking of getting mine, and they said 5-8" is ideal. I've actually heard it works better at 8". You can stack layers of egg crate underneath it to help lift it up. Mine is at 8" exactly with 3 layers of egg crate under it. My stand has 25" to work with, so I know the boat you're in.
Mesh-Mod that thing ASAP also.
Once you get it, check out this video:
CLICKY