I did all ways. Innertube, Hoses , clamps.
Clamps are the savest. The work all the time in every condition. But the need the most time. Pressure hoses are fine, but i had to learn a lot because the first try the pressure leaks and that makes you hurry.. after fixing all the weak points this works fine.
Innertubes are the easiest way. But be aware of to much heat in a heat box. They make the innertubes weak.
One way is to use the inner tube method and put the hose above it. Just secure the hose with a rope. This methoth allows you to do the layout proper. Nothing will move when the pressure starts. You also do not need a top half of the form for those who will change some details in the layout.
You can also use the inner tubes and extra packing tape (for packing parcels) in difficult places. THis can be stretched too.
Currently i have the form so small it has about 3" parallel height to the contour of the bow. So i can wrap what i want. But this does not work with the air-hose ... it will crash the form.