Usually they were hung upside down and suspended from sprung tethers to record 'lift' @ speed' by measuring how much downforce was applied to the model by the windtunnel using analog dial load gages working against calibrated springs, there's a widely circulated photo of a DC3 wooden model in the Cal Tech wind tunnel all strung 'up' with wires, the photo is flipped over when it's used as the author or editor, doesn't want to use the time and space to explain whats really going on to the great unwashed who wouldn't understand anyway.
I would guess this model as shown was to check airflow patterns around the nose and wing to body areas of the Packard installation for air intake and disrupted or turbulent air @ the wing/body interface and maybe the new radiator design too as it's got wings that STREGA would kill to be able to use, fast? OH YEAH! but very very goosey on approach and landing!!!!