Whatever you do, if you permanently mount it, look at getting a Burley Pro Mount Cover to protect your transducer.
Another option is the side mount option from Yak Attack.
There are lots of you tube videos that explore the various options. So before you drill take a chill and research it. I have a Hobie so I am spoiled; as it comes with a mount setup. Still, I had to get a Burley Pro cover to keep the transducer from getting shredded.