Stef:
Working in a room panorama I understand the tutorials prompt to add a cube after calibration. Shows accuracy.
But few rooms are a perfect cube and I have a problem with textures outside of that cube. Obscured.
Is it a sound practice to introduce the cube, model as much as possible within the cube but then delete it so that additions can be made beyond the original cube limits??.

Hello,
 
Texturing outside a cube:
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  You can hide your objects temporary:  
select your cube + (ctrl+H)    or
select your cube + contextual menu->Hide
 
To show the cube again : select it in the scenebrowser, and Ctrl+H again to switch the display of that cube.
 
Hidden objets will not be used at texture extraction step.
 
Room is not a cube:
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In place of Cubes you could use plane primitives to create your ground and walls (or even create face tool).
 
Or place a cube that fits best, part of your room, and modify your cube:
- move edges using the Translate manipulator (check the video that shows the full example)  
- split and extrude to add more complexity  
 
Best,
 
Stef