Hi jackbackintheday,
Whether it creates a hammock effect would depend on the specifics of the layers (thickness is one of several factors along with ILD, compression modulus, point elasticity, and others that can affect softness, pressure relief, and alignment, and how far you sink into a mattress with different parts of your body). There is more information in post #14 here about the effects of thickness. At 260 lbs you are likely in a range where an extra layer and greater thickness than the more “standard” 8" to 9" would be more noticeable and may be a preference or allow for a design that is more customizable (if there are more component layers) or more suitable for you in terms of PPP but like everything else connected to mattresses it would depend on the specifics of the design and on the sensitivity and preferences of the person.
Phoenix