Couldn't shrink vmdk with converter

I've red a lot of posts on how shrink a vmdk, but I don't know how to proceed. I have a 450GB vmdk containing only 40GB, ESXi 5.0 U2 and 2 datastore (500GB + 250GB). So this is what i've done:

1. i've zeroed all the free space on the OS filesystem
2. i've used 'vmkfstools --punchzero <src.vmdk>' to remove zeroed free space, now its size is 40GB (obtained with 'du -sh <path/*.vmdk>')
3. i've moved it from datastore2 to datastore1 using 'vmkfstools -i <src.vmdk> <dst.vmdk> -d thin'
4. i've repartitioned the filesystem from 450GB to 64GB

Now, what I want to do is to resize the thin provisioning of the vmdk, in order just to fit 64GB, and i've tried to do with Converter. The problem is that at the end of the conversion wizard, i can't select nothing else than option "copy all disks and maintain layout"

Of course this is not what I was expecting... but i don't know how to solve this problem.

Anyone can help me please?

Thank you,

-Mic