Pressure, hello and good day.
I see you have moisture problems with your Flat. I too have done a lot of Briskys and have no problem with dryness , however I do my Brisket things a bit differently.
I am a stickburner and work with wood only and once placed in my smoker ,it stays shut (the lid) until my temps. get to my liking ,195*F to 200*F. (see my BBQ Meat shots in my profile). I,m handicapped with my on-line shots ( my puter is down and using the Son's )
My theory is , a Smoker that leaks very little will keep the moisture in the meat and leaving it shut keeps it moister. (see my pics on my profile). I do not wrap or turn the meat as it will do fine as it sits. Be it luck or my dedicated attention to my heats(I'm rather Anal about my cooks) ,they come out great. A heat of no more than 225*F (+/- 15*f) will surely do a good job for you. My sliced Flats look juicy and have a good smokering and are tender as can be.
Good luck with your Briskets and don't give-up on the Flats , too good to pass by.
Have fun and as always. . .