Unused Potion subID (DamageValues) ?

I have written a plugin which creates custom recipes for potions. They work fine on the craftingtable and i get the right potion with the effects and lore i wanted.
Now i need to give those potions with a /give or similar command, to be able to add them into Questrewards or Lootchests.
But it seems it really doesn't matter what subid i enter on the /give command, they seem to be all currently used by minecrafts default potions, even very high numbers like 373:0123456789 is already used.
Is there any free subId i could use or any other way i can import my recipes so i can give me the potion with a default item id:subid ?

 

Potions use a variety of algorithms using their data values to determine what effects they have as explained here: http://www.minecraftwiki.net/wiki/Data_values#Potions

So in effect every data value should already be used for a potion.

You could take a data value for a potion that isn't possible to get illegitimately in the game though or you could just make your own command to give a player your potions.