You don't need a 4Gb Workbench partition. The most you will ever use for Workbench is around 75Mb maximum - and that's with every possible patch and add-on. (it's not Windows you know ;-))
I suggest you make a 100Mb Workbench partition, then make a 2Gb (exactly) games partition (2Gb is the maximum partition size when using FFS - some programs have problems with partitions > 2Gb). Always quick format. When you run out of space on your 2Gb partition (which won't be any time soon), you can make another 1.9Gb partition and still be under the 4Gb limit. If you still run out of space (highly unlikely), then you can worry about the hassle of partitioning beyond the 4Gb.
