[Renfield]

"...I remember one harpoon vs target shoot onboard the USS Harold E. Holt, we weren't the firing ship, just the observers, but the target ship had been gutted, and was basically just a steel shell. The harpoon went through the ship, about 10 ft above the waterline, and exploded about 100yds, on the OTHER SIDE.

All that precious decoy would have done, is ensure that the warhead would have exploded closer to the real target...."

Ever thought about 2 vertical planar surfaces, one on each pontoon of the catamaran?

[wyattearp]

I have a better idea:

Turn the automated missile defense system back on.

[Klutz Dohanger]

Ever thought about 2 vertical planar surfaces, one on each pontoon of the catamaran?

The naval equivalent of adding explosive charges to the barrage balloons.

[Oztrich Boy]

Ever thought about 2 vertical planar surfaces, one on each pontoon of the catamaran?

Except at 400 tons each, an catamatan won't have enough bouyancy, it needs to be a displacemet hull.
Then there is the propulsion system to get it up to 28 knots to match the missile ship

We are now talking 4000 tins, 40000 SHP - a significant target in this own right - better give it 6" guns to defent itself.