I don't believe it is possible to resize through the ovftool directly. You can resize the virtual disk using the VMware tools as described in this post: http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1004047
That handles the virtual disk but you still need to expand the guest's system/root disk. For this you can find several articles which use the gparted partitioning tool for their examples through a simple Google search.
Thanks for the help, gparted worked great.