Default 'wear' position for an item in avatars inventory...

[Driving]

How do I make it so when the user wears an item it goes to the HUD centre by default?

(Like the Fish Hunt HUD does)

[Ceera Murakami]

It isn't a scripting issue. You position the original there on yourself and then take it back into inventory before making it available to others. It will then default to where it was last worn by you for the new users, until they reassign that location. This is the same process needed for all prim attachments on the avatar itself, like skirts and hair and collars and belts.

There may be a way with LSL to force the attach position, but if there is I wouldn't use it. That would make it impossible for your customers to reassign it to another position if they needed to for any reason, such as having too many other things using that same attachment point for their viewer of choice to support. A customer who still uses a 1.x based Viewer might have another HUD that also uses that same spot, but their viewer only allows one HUD per HUD position. 

[Driving]

Ah, right thanks for that

[PeterCanessa Oh]

http://wiki.secondlife.com/wiki/LlAttachToAvatar

NB: "If attach_point is zero, then the object attaches to the attach point it was most recently attached to." (as per Ceera)