Hi Jim;
Hmm, grilling steaks over a roaring J-Tube could be problematic.
The best method might be to use a hot J-Tube with coals and add small amounts of wood once your steaks are on the grill.
You talked about being able to move this under cover.
Would a tarp be acceptable?
Consider using new clay bricks and building a traditional
rocket stove; there is no welding involved!
A clay sand mortar will keep it airtight.
A simple tarp cover will keep the rain from soaking the bricks and eventually harming the mortar.
J-Tubes are simple to build.
New solid clay bricks are easy to locate in most areas.
A bag of graded sand (home D) and a bag of dry clay.
I'll be happy to supply you with the dimensions.