I do not use the water pan at all on my 18.5...it really hangs low and restricts abiliy to stir the lump and knock off ash, add chips etc. I use a 15+" clay saucer, folied.
This does raise the bottom grill an inch but I'm using an extra purchased one that has 3 'L' brackets welded to it for the center grill stands and they aid in grill removal.
I'm considering lengthening the internal grill brackets to drop the bottom grill and saucer to reclaim some food volume, as I now have plenty of working space over the coals.
When completed I'll add photos to the MODS section.