M_Boats: Depth and Fish Finder installation on M15

I am installing a Piranha 15 combination fish and depth finder in the forward locker forward of the keel slope on my M15. Can anyone recommend a non permanent material to set the transducer in? I want to test it before epoxying it in place. The hull has a slight concave well just forward of the keel slope that I am going to test. Would it better to fill the well with epoxy to make a level spot or just use the attaching material to fill the well and hold the transducer in place? Any insights would be appreciated. Norm M15 #172