Epoxy for transucer?

Brent says in this video he uses EPOXY.  Forward to the 3:00 minute mark.

https://youtu.be/9X4CfZcrZls?t=181

The epoxy I have used in the past did not flex enough.  Plastic kayaks flex.  Any bump and the transducer pops off the hull.
Is there something different about glass?  I have a have a hard time believing this is the best idea.  Heated Marine Goop worked great for me.

Owners of Stealth glass kayaks, what glue did you use?

Thanks

West System makes an epoxy specific for plastic.  Standard epoxy works on plastic hulls that are properly prepared.  Had one in my first kayak & it lived atop my truck for several years w/o breaking free.

Water bath is best for kayaks.