Butt - I don't put them on the bottom. I put them on the rack down there where I assume rob was putting his waterpan. I have not had a problem with them rotting but I'll keep an eye on them and see tho.
Rob - for me the issue with the water is not that it messes with the airflow (although that may be true as well) the issue really is that water remains at or below 212 F (as water turns to steam and boils off if it goes above that) so your water pan will always be giving off that temp of 212 or below and helping to keep your temp down. On the other hand bricks wrapped in foil, a pan of sand, clay flower pot bases, those gas bricks that I linked or any other solid heat sink will get much hotter than 212 and give off a high temp. That is why i suggested taking it out the water may help you bring the temp up. Conversely when I run the
WSM, I can not run it without a water pan as I need it to help keep temps down at 215-235 where I like to smoke. Took me 4 or 5 smokes to get the hang of temp control in this thing as modified. At least you get to eat lots of pork during the learning process