Chop,
First and foremost they have to be bright, 150 watt HID is best.
On your 340 you need only one.
I had a Deepsea 150 W HID on my 04 360, and it was awesome.
It was the brightest in the Marina.
They are expensive but you get what you pay for.
It is my opinion that if I'm drilling a hole in my hull I'm going to plug it with the most expensive stuff I can find.
Think about it, is this where you want to get a 'deal'?
However with the HID's they are 110 volt, so you have to be on shore power or use the generator.
Without spending some serious dollars you will not get the brightness with a 12v LED.
I'm not too impressed with hanging extra stuff on my trim tabs, although I like Tom(?) Hurley having met him several times.
Now I am consdiering using the Ocean LED for the new boat and as it is wider I will go with two.
I may even use the surface mount as I'm told they are as bright as the through hulls.
Jim Conroy
2004 420 DA