I need to add some trim tabs to my plateboat as it likes to porpoise due to having a 200hp outboard. My bottom width is 72". Is there a formula or SWAG for me to go by? Not sure if I need to weld something all the way across or something on both sides. Any suggestions would be appreciated.

1 on each side 10-12" inches each about 4-6" from the edge of the boat. should do you some good.

Ive put these on several boats for guys around me.. as stated above, i did 1 on each side 12" long and 4" inside. Make sure when its done that it is flush with the bottom of the boat. I would weld them on and use a straight edge to make sure they were true all the way across. Once they are on if you need to keep the front down a little more just lightly tap down on the tabs and it will make a huge difference. Also, they only need stick off the back about 3/4"-1".

Thanks guys. So 12"×1" strip welded 4" in from the outside. Welded flush with bottom. Anything else? If not i will get busy.

Nope...Just remember that it doesn't take much when you bend them.

just get these and use a trunbuckel to secure and adjust them instead of hydraulics. I did this on my wooden boat and it worked very well. You are not married to a fixed position. You can ride around to test and just reach over the transom and turn the turnbuckle to adjust accordingly. You can also adjust to accomodate the weight distribution in your boat when carrying a heavy load.

http://www.westmarine.com/buy/bennett-m ... 89_001_510