Hi Michael : Welcome to Permies!
My shop is 24 x 32 with tall ceilings and badly leaky doors. Heated it with a double barrel stove for 20 plus years, here in northern Montana . I could have that stove roaring (the
wood gobbler)and over by the doors your wrench would stick to your hand. Shop cooled off 30 minutes after the stove died out.
Took that stove out this summer and it is being replaced by my new brick bell
rmh shop heater. (permies.com/t/94980/Brick-Bell-Shop-Heater) It's still under construction ... wish I had started building in May!
It's not a batch box but an 8" J tube. There is a small possibility that I might change it out a batch box in a year or two, if I am unhappy with its overall performance.
Most brick bell
rmh's do not use a barrel . I designed one in because, like you I want instant quick heat I also want that heat stored for more than 30 minutes.
Lots of possibility's with a Rocket, you just need to decide which one is right for you.
Do you have a copy of the Builders Guide ? I highly recommend one!