There is a bit weird way to create VMs using vCloud APIs:
Preparation
1. Create a diskless VM inside a vApp
2. Turn vApp into template
3. Instantiate the template in to new vApp with single VM and no disks. OR use recompose to add new VM to existing vApp Or compose to add the VM into new vApp (I am not sure if you can add same VM many times in one call)
4. Add disks and update HW settings to suit your need.
If you want to strat off wihtout the preparation
1. Download the vApp OVF file using API
2. Check the OVf for any vmdl references there should be none.
3. Instead of steps #1 and #2 above upload the OVF file as template.