You can use 2 or 3 jacks nailed to the king. 2x studs are 1 1/2" thick-two together = 3". That is all that is required to transfer load from a correctly sized header / girder. Triple 5.5" x 1.75" bolted together for the 16' door and 8' door.if you wanted to add a third jack,consider the 2x10...
HEADERS REQUIRE 3" BEARING,DOUBLE JACKS MEET CODE TRIPLE IF YOU LIKE
IF YOU CAN, DOUBLE UP ON YOUR PLATES. DRILL A 1" HOLE AND CUT FLUSH ANY THREAD THAT STICKS UP.
HEADER HIGHT SHOULD BE AT 8' 2 1/2" O.F.F. THIS ALLOWES 2X JAMB, 1X TRIM AND DOOR WEATHER STRIP.
ENJOY YOUR NEW "HOME":beer: