Feasible to run pool of v2 and v3 IdP servers?

[shibboleth655 at lewenberg.com]

We are working on our Shibboleth IdP v2 to v3 upgrade. Currently, we 
have a load-balanced pool of v2 IdP servers. We are thinking to bring up 
a new IdP v3 server and then add it to the pool of v2 servers as a first 
test. Would that work? Has anyone done that?

One issue that crossed my mind is how v3 encrypts cookies using the 
DataSealer. How would we handle that in a mixed environment?