I would get the Helix G2N series so you can link both units to one ducer. If you've already bought the Helix and it's not the new networking model, I would mount it where you can see it while driving the boat so you can get the boat positioned before switching locators. The Helix will be way more beneficial in finding spots than your Optima.
Also, if you don't have a universal transducer in your trolling motor, do yourself a favor and get a Transducer Shield & Saver. It is a metal housing that holds your ducer to the bottom of your trolling motor housing and keeps you from breaking the plastic mounting arm on the ducer. They run about $40, but protect your investment and are only a third of the cost of a new ducer! I've been running one for 4 years now and it works great!