Harpooner might be half the strength of a normal ship, say a frigate, come at about the same time, and be +100% vs living units, and be slightly cheaper.
Or conversely, could be 75% str of a frigate, +50% vs living units, and cost the same (or a slightly higher percentage, say +60 or +70 vs living, and cost more ... if its +100% it should cost double that of a frigate).
I rather like the first idea, myself, as I can't imagine a Harpooner to do well at all vs a Frigate. However, if you want the first idea to be stronger, increase the bonus to 120 or 150% vs living.
Or conversely, could be 75% str of a frigate, +50% vs living units, and cost the same (or a slightly higher percentage, say +60 or +70 vs living, and cost more ... if its +100% it should cost double that of a frigate).
I rather like the first idea, myself, as I can't imagine a Harpooner to do well at all vs a Frigate. However, if you want the first idea to be stronger, increase the bonus to 120 or 150% vs living.