WOW with the two wheeler sitting there the tank shows its size. When it was out front I sure didn't think it was that big. Have you ran the numbers on the pit calculator? You can enter the tank sizes you have and it will tell you what size you would need for the air openings.
You may check online at a volume calculator site and see just how much smaller the small tank is.. I think most try to go with 1/3 smaller for the fire. Now that does not mean 1/4 smaller would not work. You may have to tend it more often tho.
I have been wondering if a tank like yours would work set up like a UDS. Have the basket in the bottom, only difference would be the door vs a lid. You would loose alot of heat when ya open the door but heck if your lookin you ain't cookin.
Just a thought.
Good Luck and pls keep us posted.