I have always been able to use SUSE's automatic partitioner. Works great, never had a probem. I always ended up with a dual-boot.
And as you can tell from my signature, I have had to reinstall a few times while learning how to that many os's on my machine.

If you have an unformatted partition, SUSE will use that.
If you want SUSE to resize your Widows partition, it can do that.
You just have to tell it what to do.