Transducer mount material

[abl1111]

Want to add a transducer mount to mount my transducer to the hull. Been looking into different materials and can’t find anything conclusive. I have prepped a piece of Azek but I’m concerned that it might be too soft and water flow might rip the transducer off. Anybody have experience with mounting material ? Whatever material, I’m going to screw it into transom after potting holes...