I tried modifying a AT9 dish for a slimline LNB and had little success. I think the arm legnth may be different. I cut a notch for the LNB to fit and still had trouble peaking it, just gave up and bought a slimline dish off craigslist.
As for setup, option 18 under dish type is a SWM slimline-5 setup. There is also a SWM slimline-3 setup for the LNB that doesn't have 110/119. Selecting the right one determines where it gets the guide data.
Remember to NOT use B-Band converters.
Also, if you have trouble getting to the satellite setup after restarting the receiver (assuming you unplug the power when you change the LNB - recomended), you may need to let it sit at searching for signal for 5 mintues or so, then the menu button will give you the option for satellite setup.