what i did for triple boot, i only used bootcamp to get the drivers, i partitioned with disk utility
0) partition drive into 3 parts (osx at 20gb, 20gb empty hfs, rest as fat32)
1) install refit
2) restart computer 2 times (until refit shows)
2.5) in refit menu go to partition manager and sync the MBR
3) turn off machine, insert windows 8.1 live usb (made using official windows 7 live usb creator), install bootcamp 5.0 drivers
4) turn on machine, pick usb from refit menu
5) install windows 8.1 (ends up as legacy boot)
6) turn off machine insert linux live usb
7) turn on machine pick usb from refit menu, install linux with eif grub2
now when you restart you should have all three operating systems to pick from in the refit menu, alternatively you can boot into osx and remove refit and you will just have to use the 'hold alt' option to pick the operating system
you cam mimic the above and leave out the linux parts to get osx + windows 8.1
alternatively:
0) use bootcamp to partition and make live usb and get divers
1) restart holding option
2) install windows 8.1
3) use hold option to pick windows (or install refit if you dont want to have to remember to hold option)
problems:
when you are installing windows 8.1 remember to 'format' the partition even if it is already ntfs, sometimes deleting the partition and creating a new one will help - else try go into osx, disk utility and delete and create the partition again (this fixed windows 8.1 "can not update boot configuration" for me)