Bootcamp off an external drive with multiple partitions?

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I have a 1 terabyte hard drive (not ssd) that I use for time machine backups. My MacBook Pro has a 256 gig ssd and I'd rather not make that any smaller. Right now, I'm booting windows off a usb3.0 thumb drive, but there's not much I can install, owing to its size. I was wondering if it'd be possible to partition my time machine drive into 2, a 700 gig partition for time machine and a 300 gig partition for bootcamp. Would this work? I tried googling and I couldn't find anything relevant. Thanks!

 

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Finally got around to doing it. Turns out I had to reformat my drive to change it from MBR to GUID but after that, I allotted 250 gigs for a bootcamp partition and 750 for time machine/general use. It works just fine. The only thing I don't like is moving back to a hard drive. It's like the platter is suspended in fudge - it's so freaking slow compared to the ssd I've gotten used to!