No, that was just for the cars. They had intended to run the bikes on the full Gordon Bennett course - Quarter Bridge to Castletown, up the Ballamodha, straight on at Ballacraine to Ballaugh, where they turned left to Old Ballaugh Church then through Sandygate to Ramsey, through Parliament Square and across the mountain to Quarter Bridge (there was no Signpost corner section, they turned right at Cronk ny Mona and through Ballanard Road to drop down Bray Hill. That course was found to be too demanding for the single-speed belt drivers so they used a shortened version.
In the early days of racing at Jurby airfield, the length of the circuit, particularly round the hanger section, depended on how many concrete blocks had been made and parked alongside the course!