The internal keel, tanks, and sub-sole on a Caliber are actually integrated as part of the hull. The keel is not just bolted on, the sub-sole doesn't just support furniture, and the tanks are not just dropped in place. Each object is heavily bonded into place. We call this method our Integral Strength-Grid system. Compared to the other boats, our integrated structure offers many significant advantages:

A deeper bilge prevents water from sloshing into lockers while the boat is heeled.
No external keel bolts to maintain or cause leaks.
Weight of keel and primary sea loads are evenly distributed throughout entire grid structure.
Integral FRP tanks enhance the hull's strength, and serves as a double bottom that can prevent flooding if the hull is holed at the location of the tanks.

Ballast is double-sealed within the keel as a safeguard against flooding if the keel is ever holed.

Integral Strength-Grid System™

Water-tight Collision Bulkhead heavily glassed in place bonded to the hull and the structural dividers forward of it. This creates an extremely strong matrix structure.
Integral tanks, lids, and baffles add strength to the subsole structure to help spread loads evenly over hull. Because the lids will be heavily bonded in place, any surface are of the tanks, will act to form a double-bottom.
Structural sub-sole will be laminated around it's entire perimeter adding a complete bonding between grid structure and hull. Bonding all structures together. Keel, engine, and primary sea loads will be spread evenly over entire bottom surface area.
Stringers are heavily glassed into position with extra heavy laminates and resins. Entire grid structure acts as a single strong unit.
Michael Kasten of Kasten Marine Design in Port Townsend, Washington with over 20 years of boat building and design experience says,
               "Integral tanks provide a number of design benefits. Consider the following:
--They prevent the volume lost with separately installed non-integral tanks.
--They eliminate the dead space present around non-integral tanks, thus abolishing yet another place where water and objects can collect.
--They reinforce the hull with baffles and tank-faces that are attached to, and therefore reinforce the hull skin.
--They create a double-bottom beneath the sole so damage to the hull where the tanks are located won't compromise the watertight integrity of the vessel. In other words if you puncture the hull in the tank area, you will lose the fluid in that tank compartment, but the boat is not likely to sink."
From “There Are No Maintenance-Free Metallic Fuel Tanks” by United States Coast Guard Boating Safety Circular
               “While FRP fuel tanks [integral fiberglass tanks] have proven their effectiveness, they are very labor-intensive to produce, making this option time-and cost-prohibitive to many of the high volume manufacturers of low and medium priced boats.”
Yacht designer Paul Bieker of Seattle, Washington says,
               "Integral tanks and their baffles provide structural strength to the hull," he continues "Non-integral task provide the opposite, by creating a void where structure cannot be." Further Bieker adds, "As a teenage, I spent a year and a half cruising down in the South Pacific," he concludes, "while anchored in an atoll, we were hit by a surprise storm that knocked a fiberglass boat into the coral. It was hold by a metal fuel tank, and sank. The fact that the boat my not have been lost if that tank was integral made a lasting impression on me."
From "Offshore Yachts" by John Rousmaniere
             “The sides and tops of integral tanks can add to the longitudinal strength and stiffening of metal and fiberglass hulls if they can be arranged to be continuous over a reasonable distance, or at least between structural bulkheads.”