Russ, I don't know if the measurements are different on a 1999 coach but on the early 1990's Newells, ride height should be 12" from the ground to the bottom of the square tubing just up inside the sidewall of the coach just behind the front wheel well and just in front of the rear wheel well. The travel height valve linkages are adjustable and that is what you will need to do if you have significantly less ground clearance. For more information see
http://www.newellclassic.com/forum/showthread.php?t=389
With the long wheelbase of the Newell, it is possible to drag high center. I have had several occasions where I had to press and hold the RAISE button to get the coach up as high as possible to avoid dragging the center of the coach. Make sure you do not attempt to move the coach more than about 5 mph when using the DUMP or RAISE buttons. Be particularly careful when using the DUMP button. The rear wheel flares will rub on the rear drive tires and the front tires will be severely limited in turning radius before the tires begin to rub so if you really want the front down low keep the front wheels pointed straight ahead. Also remember that the dump and raise takes place slowly. To expedite the process, put the coach in neutral, hit the fast idle switch and let the engine driven air compressor have a fighting chance to put some air into those air bags. You really need to keep the air pressure at or above 80-90 psi to get the lift to occur during a reasonable time.
If anyone is interested in me uploading and posting a link to the HWH Air Leveling System Manual from 1999, let me know.