Detecing Unit Size

ok what Im trying to do is make a unit grow each time u feed it food, I have this trigger done;

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Feed Pig Water
Events
Unit - A unit Acquires an item
Conditions
((Unit-type of (Triggering unit)) Equal to Pig) and ((Item-type of (Item being manipulated)) Equal to Water)
Actions
Animation - Change (Triggering unit)'s size to (3.00%, 3.00%, 3.00%) of its original size
Item - Remove (Item being manipulated)
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now what I need to do is detect the biggest pig out of 5 at the end of 25 mins
I can't figure that one out.

ok, I got the detecting part done but now I need to be able to tell which one is the biggest, this is the trigger I have so far;

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End Pig Contest
Events
Time - Timer expires
Conditions
Actions
Countdown Timer - Destroy (Last created timer window)
Game - Display to (All players) the text: TIME IS UP!!! The j...
Unit Group - Pick every unit in (Units in (Playable map area)) and do (Actions)
Loop - Actions
If (All Conditions are True) then do (Then Actions) else do (Else Actions)
If - Conditions
((Unit-type of (Picked unit)) Equal to Farmer) or ((Unit-type of (Picked unit)) Equal to Pig)
Then - Actions
Unit - Move (Picked unit) instantly to (Center of StartEnd <gen>)
Else - Actions
Unit Group - Pick every unit in (Units in StartEnd <gen>) and do (Actions)
Loop - Actions
this is where I need the help
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anyone??????????? :(