Different Exchange Certificates for CAS Array supported?

Hi,

I have 2 CAS servers using NLB to form a CAS Array, and our client do not allow the private key to be exportable when generating the Exchange certificate request. This means we need to request one Exchange certificate for each CAS server since the cert cannot be imported

1. is this a supported configuration?

2. can we assign Exchange services to 2 certificates?

thanks!