With the #Coaxial8or [gd0144] installed, I've gone to the limits (of the printer) to get this information.

Motion limits

// The size of the printable area
#define X_BED_SIZE 308
#define Y_BED_SIZE X_BED_SIZE

// Travel limits 
#define X_MIN_POS 0
#define Y_MIN_POS -9
#define Z_MIN_POS 0
#define X_MAX_POS X_BED_SIZE
#define Y_MAX_POS Y_BED_SIZE
#define Z_MAX_POS 328

308 x 308mm is where the nozzle is just inside the edge of the bed for my printer. Due to the bowden tubes for the coaxial8or, I've only gone up to 328mm. It seems that I can comfortably  do something like 305 x 305 x 325mm, which is essentially a 12 inch cube with Z height to spare; I'm satisfied with that. I still get to use the full advertised XY bed size for the CR-10 and I don't think I've ever had a single print even 250mm high, let alone the 400mm that a stock CR-10 supports. Like I've said in this Coaxial8or R1 log, I've tried hard to preseve my XY limits, even going as far as the #Revolving Hotend [gd0012] so that I didn't lose any to XY nozzle offsets. 

I should mention that I've got a custom Y tensioner installed, which allows an extra 10mm or so, hence the negative Y_MIN_POS. It would likely be decreased to -6 if one was to install the slimmened Coaxial8or R1.

SanBrother DDE (BMG clone) 

//#define DEFAULT_AXIS_STEPS_PER_UNIT   { 320, 320, 1600, 1675 }  // 64 microsteps
//#define DEFAULT_AXIS_STEPS_PER_UNIT   { 80, 80, 400, 418.750 }  // 16 microsteps
#define DEFAULT_AXIS_STEPS_PER_UNIT     { 80, 80, 400, 209.375 }  // 16 XYZ, 8 E microsteps

 This agrees with my previous go-to value of 418.5mm that I must've calibrated years ago when TriangleLab first came out with their BMG clone and have used it blindly with every BMG clone since. Now I have a more accurate value, obtained by going up to 64 microsteps and no interpolation and getting 99.97mm when expecting 100.00mm. I've then dropped the E to 8 microsteps, mainly because there's eight of them and I don't want to find out that the 180MHz chip on the Octopus Pro can't handle that kind of step rate, but also because of the below graph from this video:

This is for the TMC2208 (not the 2209/2226 I've got) and the lower microsteps were 1/4 not 1/8, but I'm just kind of assuming that the torque curves between StealthChop and SpreadCycle are more similar at 1/8 than 1/16.