on max.
Best way is trial/error method..
place it on max, export it as lom, drop in the shapes folder, check.
If its high move model a little lower and try again. Its a long work for the first time but when you figure it out its easy. And a tip..Always use afterburner to place (measure) the plane right.
Lets say you replace A-10
open meinit.xml
find this line "<Plane CLSID="{8FDB2742-2283-450D-B417-CFC47774E8B6}" Cannon="yes" EmptyWeight="9389" HumanCockpit="yes" MaxFuelWeight="4853" MaxHeight="10000" MaxSpeed="834" MaxTakeOffWeight="21081" Name="A-10A" Rate="50" Shape="a-10" WingSpan="17.53" WorldID="17">"
For any other plane, line is almost the same but name section and values change
from there scroll down until this line
"<Pylon FiZ="-3.3" Number="1" Type="0" X="-0.22" Y="-0.062" Z="-5.522">"
the x here represents forward / backward placement.
y is for up/ down
and z is for left/right.
the " Number="1" " means you are at the first pylon.
You start changing values and go to the game and check. Its a nasty work, worse than placing the plane. When you satisfied with the place of the first pylon move to the line where it says Pylon at the begining of the line and the Number value is 2 then 3 etc.
Tip: When you place the pylon location, try different rockets to double check the place. And when you placed half of the plane you can copy the same values for the other side of the plane. You just need to erase "-" from the z value.
Hope this helps..
If you still have problems just whistle :)