i used ram for a while - but recently switched kayaks and switched over to using FishfinderMounts - Magnetic
It is not the cheapest option - but it fits my needs.
I attached the inside magnet to a cord and tie that off to my hatch - then place the magnet where-ever i please. holds on to my Lowrance Totalscan transducer w/o any issues.
That said the magnetic mount works well for me because i flip between two different yaks and a porte-boat - so the magnet makes it nice and easy to move from one to the other.
Other nice things for the magnet
1) can adjust position based on "type" of fishing you plan on doing
2) it is a "soft" but strong holder - you hit anything in the kayak and the magnets will "give" and prevent a lot of damage to your transducer unit... or if you hit hard enough they will just detach. I keep the transducer rigged to a paracord so that if that does happen the transducer cord doesn't take all the weight.
I have knocked it in both my kayak and my boat - not even a scratch to the transducer yet (though they were softer knocks). The magnets hold even up to 12-13mph in my boat off the transom - and i still get depth and decent DS.