Three Tube; Four Tube Cat Chassis. We've got Ya Covered.
When One Contemplates the Cost of the Inflatable on a $ / Lb Displacement, the obvious choice is RowFrame's War Pony (featured above.)
Three tubes offers a 50% increase and 4 tubes a 100% increase over the conventional cat chasis. For Day Tripping, Omit the Center Tube for crawlin over the rocks. The version illustrated is modular. These are also available with end welded fittings attaching to 1.25 NPS and 1.5 NPS Longitudinal Stringers.