The flat keel of the X-Factor can be used to your advantage. There is a spot just aft of the rear hatch that is flat and almost level. It is a great spot for the transducer because it is always going to be in contact with the water, has smooth water flow and is out of the way.
I had room for two transducers (don't ask
). I've now got a larger Lowrance transducer mounter there. It fits well and I get acceptable performance.
You might want to put some shims under the hull to level it out before installing the transducer. You don't want the transducer to move once it has been seated in the Goop. You can tape it down or just level the hull. I usually make a mess of the tape and move the puck too much. I'd rather just level the hull and let the transducer sit, undisturbed, until the Goop cures. I also use zip ties to suspend the transducer cable before I apply the Goop. The weight and bend of the cable will want to twist the transducers in the Goop. By securing the cable with a neutral bend in it there is less chance of the transducer moving.
Sanding the hull surface will improve adhesion. Just make sure you thoroughly clean and dry the area before applying the Goop.
Have everything prepared before you put the Goop down in the hull. This will make the installation go more smoothly. Have the hull level and stable; surface prepped and cleaned; cable in place; and dry fit the transducer. Once you are satisfied and everything is ready to go you can apply the Goop.