Set VPC when creating a server on AWS via Forge

I have a few EC2's running in VPCa, including my RDS instance. When deploying a new server from Forge on AWS, Forge (creates?) a new VPC, say VPCb and deploys it there, making it impossible to use internal IP's to my RDS in VPCa.

Is there any way to have control over this behavior? Or is nothing left to do but use the Custom VPS mode...