Hmm. Your posts are a little ambiguous to me so I just want to clarify. I hope you have already partitioned your drive into two partitions *before* you installed windows. Maybe I missed something, just trying to make sure you aren't messing something up
I would. As i have been doing it for at least 7 years this way. Never lost a single partition table using GParted. I trust in it so much i recommend it to all and even wrote up a full guide with pictures.
Who ever told you that it was risky business using Gparted to shrink a NTFS partition using GParted certainly didnt use it properly or fully test it out on multiple machines with multiple people. I have yet to find someone who couldnt use this guide to shrink a partition and still have it be used.
If I know in advance that I am going to need to install more than one OS then it makes sense to partition the drive before installing the first one. If the first one is already installed then there is only one option remaining - shrink a partition.