Dronekit-sitl in python, troubles selecting the right model

I am trying to configure my simulator to run quadplane.

The Good news:
I Can use sim_vehicle.py and get the vehicle I want and I can connect to it using mission planner, upload a vtol mission and off we go. sim_vehicle.py creates a bin in build/sitl/bin and parameters in Tools/autotest/ there is an emrom.bin all is good.

The bad News
I then think fantastic, let me now access this from inside my python script running dronkit-sitl and no joy its not the model I created and the params are not the same etc etc.

Here is my connect code
import dronekit_sitl
from dronekit_sitl import SITL
log(self.sqlcon,‘WARNING’,‘No autopilot found I will start SITL’)
os.environ[“SITL_BINARY”] = “/home/pi/ardu/ardupilot/build/sitl/bin/arduplane”
os.environ[“SITL_DEFAULTS_FILEPATH”] = “/home/pi/ardu/ardupilot/Tools/autotest/default_params/quadplane.parm”
sitl = dronekit_sitl.start_default(51.5546443,-0.1804483)
connection_string = sitl.connection_string()
# Connect to the Vehicle
log(self.sqlcon,‘INFO’,‘Connecting to vehicle on: %s’ % connection_string)
#self.plane = connect(connection_string, wait_ready=True)
self.plane = Plane(connection_string)
log(self.sqlcon,‘INFO’,“Failed to connect to SITL”)

I cant seem to find a guide for running a compiled vehicle from within a python script, and guidance or hints please??

Kind Regards,
Gus Fraser