Ahhhhhh (lightbuuuulb) - is that why perhaps your saying I would need to finish the other area to use it as a booth? Since if it's a spring and someone is jamming on the drums in the adjacent room - this area would be picking up a lot of residual sound energy from that room.
Yup! You got it. If you are standing inside the "spring" of the MSM system, then you are in the acoustic war zone! Don't forget that that's a two-way street in there: It's two different MSM systems at once: one with respect to the CR, and the other with respect to the LR. So there's two different wars going on at once. If you are in there, then you only have one leaf between you and each of those noisy things, but also you are part of the dueling MSM battle zones. That's probably not a place you'd want to set up a mic to record vocals!
I guess then it's only an issue if I plan to record in that small hallway rather than use it for storage. For storage it would be fine to leave it without Sheetrock?
I would drywall it regardless: If you don't, then anyone walking through that space is only one leaf away from either room: a cough, a sneeze, a cell phone ringing, a chat with the guy walking next to him, things getting dumped on shelves, dragged off shelves and dropped on the floor... I think you get the picture!
I may need a few pointers here. I've been doing some research over the past few days on Ray tracing
OK, it's easy and hard!
Easy in concept, hard in the sense of boring, repetitive, figuring angles, drawing lines, figuring more angles, drawing more lines, rinse, repeat....
The basic idea is this: Start from the acoustic center of your speaker, then looking directly down from above, draw a line at 90° to represent the acoustic axis. Then draw some more lines angled at 10°, 20°, 30°, 40°, 50° and 60°, going BOTH ways: to the left and to the right of the axis. Now follow each line in turn across the room, to see what it hits: wall, window, door, another speaker, etc. At the point where it hits that surface, figure out the angle of incidence, then draw another line bouncing off that surface starting from the very spot that the first lie touched it, but at the exact opposite angle. For example, if the incoming line hit the surface at 27.3°, then the reflected line must bounce off at 27.3° going the other way. You measure all of these angles with respect to the "surface normal", which is just a fancy way of saying "a line poking out of the surface perpendicular to it, at the point where the incoming line hit it". You always measure all your incoming and outgoing angles with respect to the "normal".
So, then you follow this new reflected ray across the room again, to see where it goes: Hopefully it heads off to the back wall, where you will absorb it. It might also head off towards another surface in the front half of the room, in which case: "rinse, repeat".... same procedure for another bounce.
As you follow each line, you want to make sure that it does NOT get close to your ears at he mix position! That's the entire point of the exercise. So draw a circle at the mix position to represent the size of your head, then draw a couple of bigger circles, about 1 foot radius and about 2 feet radius. Ideally, you want no rays at all passing through the 2-foot circle, and definitely none in the 1-foot circle. If a ray gets into the 1-foot circle, then you need to change the angle of the surface that the ray bounced off and rinse-repeat until the ray no longer gets into the circle. It might not be possible to keep all rays out of the 2-foot circle, but do your best to minimize them, and keep them just passing through the edges, as far away from the 1-foot circle as possible.
OK, have you done all that, and gotten all your rays out of the circles by carefully angling the walls, doors and windows? Great! Now it's time to do it all again, but this time starting with a SIDE view of your room, instead of the top view. This time you'll be making rays that spread out upwards and downwards from the acoustic center of your speaker, towards the ceiling... and towards the desk, console, video monitors, etc.
When you are done, you'll have dozens of lines running all over the room in all directions, both vertically and horizontally, but hopefully there will be a clear area around your head at least 12" to 18" on each side of your head, and with a bit of luck, as much as 24" each way. But 24" is really hard to do in a small room.
OK, adding to the above: If you do find lines that are getting into your 2-foot circle (actually, it's a 2-foot sphere, really, since it goes out in all directions...) then you can also do a bit of "devil's advocate" prioritizing, by seeing which ray it actually is, and deciding if you will allow it to live or not... If it is a ray that started out with an angle of 10° or 20° from the speaker, then you really cannot allow it, since that is practically on-axis for most studio monitors. If it started out as 60°, on the other hand, then it's probably not too much of a problem, since that is pretty far off-axis, so it is going to be a mostly lower frequencies on that path, which are probably not too directional anyway.
Don't forget that each time you change the angle of a surface, you need to go back to Square One with this whole procedure, and start again, since you might have also moved some part of the surface into a position where a different ray now also hits it, at a different point....
rinse... repeat ... rinse ... repeat....
Did I mention that this is boring?
- Stuart -
I have rotated the CR 90 degrees counter clockwise which allows me to add the door away from the bass trapping area. 
so i did want to cheer you a bit, keep up the good work andy, stuart, again, this is really helpful!