In the mini you do not need to use a water pan. The mini will hold temps without issue just by adjusting the bottom vents.
I'm not sure if you cut the bottom of the tamale pot out or if you just drilled the holes. If you drilled the holes, the bottom already acts as a difuser. If you cut the bottom out, you can use the steamer insert that came with the pot as the difuser.
In my mini with the bottom cut out w/ the steamer insert as a difuser. I can maintain temps from as low as 230 and as high as 350+
*Weber Mini WSM x2 *
*Weber 22.5in OTG x2 *
*Weber Touch and Go Performer *
*Sublime Smoke UDS*
*Maverick ET-732 * World's Fastest Blue Thermapen *