I can be tricky especially in dodgy seeing. I find a hartmann mask helped when initially learning to focus. But once you've picked up what to look for then it isn't always necessary.
Do a bit of search through the solar system forum for saturn and jupiter images taken with the LPI. You'll get a more realistic idea of what can be achieved. I was using a ToUcam which has different pixels sizes so the resolution is slightly different.
Heres a few from a search
http://www.iceinspace.com.au/forum/s...&highlight=LPI
http://www.iceinspace.com.au/forum/s...&highlight=LPI
http://www.iceinspace.com.au/forum/s...&highlight=LPI
http://www.iceinspace.com.au/forum/s...&highlight=LPI
And lucky last
http://www.iceinspace.com.au/forum/s...&highlight=LPI