Just in case anyone ends up in this situation, as it's unique to Apple hardware.

Summary: Basically you can't use a disk larger than 2.2TB at all for both 
Windows and Mac OS dual booting. You could use a disk larger than 2.2TB as a 
Windows only boot disk, but it will be limited to 2.2TB. And I do mean disk, 
not disk partition. You can't get around this with partitioning.

Assertions:

1. MBR has a fixed number of sectors, which with a 512 byte sector translates 
into a maximum addressable quantity of 2.2TB, there is in effect a 2.2TB limit 
for MBR disks.

2. Apple's firmware is based on Intel EFI 1.10. Windows Vista and 7 support 
BIOS and UEFI 2.x firmware for booting, and do not support Intel EFI 1.10. [1]

3. Windows will only boot from MBR disks when using BIOS.  And it will only 
boot from GPT disks when using UEFI. 

4. Regardless of whether Windows boots BIOS or UEFI, it can use MBR or GPT 
non-boot disks.

5. Apple's CSM-BIOS requires an MBR disk. [2]

Conclusion: Since EFI 1.10 doesn't meet the UEFI 2.x requirement, the only way 
to boot Windows on a Mac is with the provided CSM-BIOS implementation. Since 
CSM-BIOS boot requires MBR, and because Windows BIOS boot requires MBR, there's 
no obvious way to use a disk larger than 2.2TB for booting Mac OS and Windows.


[1] Windows 64-bit is needed for UEFI 2.x booting.

[2] It requires either MBR only, or hybrid MBR (plus GPT). Hybrid MBR (plus 
GPT) is non-standard according to both the UEFI spec and Apple's own 
documentation. They should be treated only as an MBR disk but how they get 
treated varies a lot. Arguably Apple's treatment is inconsistent with their own 
documentation. See the last sentence in the Protective MBR section of 
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