If inbound CNAM is important to you, instead of having GV ring the OBi directly, forward it to a DID from a service provider that has CNAM (use SP2 to register to that provider). AFAIK, there are no free ones. An Anveo DID (Value @ $0.99/mo. or Unlimited @ $1.99/mo.) may be suitable; there are dozens of other choices. You could still use GV for free outbound domestic calls.
If outbound CNAM (displaying your name to people you call) is important, you will not be able to use your GV number for those calls. Providers with outbound CNAM either charge per minute for outgoing calls, or have a monthly charge for "unlimited" calling.