The design of Free Power Turbine (FPT) & Aero-derivative Engine core which enables reduced foot print, high efficiency, quick engine swap, and less cost of ownership is in times of need for LNG customers. FPT as the name states, Free spinning Turbine, facilitates the gas turbine to operate at part load with varying speed & power while maintaining high efficiency and gearbox less architecture. This gas turbine is suited for both mechanical drive & also power generation applications. This paper describes the experience of Baker Hughes, a GE Company (BHGE) in design of Turbine Rear Frame (TRF) for such an Aero-derivative gas turbine which has an FPT architecture complying to the product requirement needs. The main functional requirements of TRF is to enable the hot flow path to recover back pressure, embedded reverse thrust pressurized air, bearing sump air, oil & vent piping, and structural stiffness to with stand normal operating & emergency bearing loads. Contribution of temperature gradients related to gas turbine operating profile and corresponding cooling flows on TRF is an important aspect which would drive the structural integrity and deciding factor for fatigue life of the whole configuration. During designing the TRF and its subcomponents, tradeoff study has been conducted for the strut configurations, cooling flow circuits and are evaluated against the structural integrity of the component. Such aspects on how various configurations are traded off would be dealt in this paper, with an added aspect of Manufacturability & Cost variations.