Recommended #' of wan subnets in vcloud?

Hello, I was wondering if two /28 wan subnets will suffice for a PoC of vCloud? each /28 gives us 8 usable public IP's, so I suppose that we could use:

1) management wan subnet:

load balancer(s) vip's, vcloud cells, management network

2) cloud tenants external network:

public IP's for consumption by the tenants (provider external networks)

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Would it make sense to use a larger wan subnet, ie. /27 or /26, to avoid wasting the network address/broadcast address of each block? In the case of a shared wan subnet, what kind of L3 routing would be needed, to achieve separation of the management VLAN's from the cloud tenants VLAN's?

Thanks!