Old dog new tricks

It was finally time to do a brisket on the 14.5. For two decades, I enjoyed the 18 WSM and used charcoal-usually Kingsford.
Now in 2018 I'm using a petite 14.5 and lump. Wow, it is different. For months I trusted the weber thermo...it seemed to stay at 250 with all vents open with charcoal.
I finally checked to find out I was 50* off. Oooops.
So now I'm using lump and cooking a full brisket packer (half on one shelf, other half on the second shelf). It came to temp nicely and settled at 265.
about 7 or so hours later it drops to 150! That wasn't expected. I guess the ring only holds so much lump. So I filled the ring with lump and lit a partial chimney.
The Wsm ran right up to 220. I closed the vents down about to about 65% open on all lower vents. Off I went only to return to 335 temps. Despite closing vents to only 40% open or so, it ran HOT. It wasn't a big deal with cook. I foiled the beef at 180 and pulled at 202.
The brisket was wonderful.

So I wonder out loud, is lump that finicky?
Has anyone made an oversized charcoal ring for the 14.5?
Oh yea, the new Smoke thermo is fabulous.

I love my 14 and do most of my personal (me & my wife) cooking on it, my 30 year old smokey joe and a refurbed 18" OTG. At this point, the 18 & 22 WSM's only get used for parties, events or comps.
For me, I stick with briquettes for the consistancy. I use kingsford pro from BJ's, and love the heat & flavor.

Next challange... Try a Flat, a small butt, and a rack of ribs in one cook. I tried. It was alot of fun. I didn't get everything perfect, but I learned a great deal.

Brett