Roof trusses are engineered to carry loads over the top chords. The diagonal web members are in compression and bottom chords are actually in tension - resisting lateral forces.
Your trusses could very well work and I could do a quick calc to qualify the loads for you - but not knowing the Ericson 23 weight, existing live and dead loads on the structure and assuming the truss design, is risky business at best.
Perhaps others will chime in with creative alternatives to support the boat from below.
True Blue . . .
sold the Nauticat