Buying my first new pair of fins for my 7"4 advice please!

Okay guys Im about 137 pounds and my board is 7"4 and the fin setups are plugs
Now I tried to search online but can't find anything regards of the length of my surfboard and what type of fin setup is best. I was looking at a thruster setup like these http://www.surffcs.com/shop/surf-thrust ... -3-tri-set
Or I am not sure if a single fin + 2 $5 side bites would suit me better? I have been surfing for the past 4 months pretty diligently and last month I broke my center fin and need a new set for Christmas.
Also guys what is your experience buying off brand fins? There are quite a few off brand fins on amazon and some do not have a website and basically sell them half the price of fcs brand. Like these
http://www.amazon.com/gp/product/B00KE6 ... _i=desktop
If these are any good I could save $40 bucks for buying them but they would probably be between medium and a large fin.
Okay guys I know I asked allot but I appreciate it!
Now I tried to search online but can't find anything regards of the length of my surfboard and what type of fin setup is best. I was looking at a thruster setup like these http://www.surffcs.com/shop/surf-thrust ... -3-tri-set
Or I am not sure if a single fin + 2 $5 side bites would suit me better? I have been surfing for the past 4 months pretty diligently and last month I broke my center fin and need a new set for Christmas.
Also guys what is your experience buying off brand fins? There are quite a few off brand fins on amazon and some do not have a website and basically sell them half the price of fcs brand. Like these
http://www.amazon.com/gp/product/B00KE6 ... _i=desktop
If these are any good I could save $40 bucks for buying them but they would probably be between medium and a large fin.
Okay guys I know I asked allot but I appreciate it!