The way it is done in GP is to give you the maximum protection against stuck notes. e.g. you play a C3 Note On, before releasing the key you transpose by +2 and you will release the key producing a D3 Note Off and the C3 will play forever… That’s why Notes Off messages are sent.
If I remember well I made a transpose Scriptlet which should be able to do what you want. It should be in the following rackspace:
