Partial Morphing

http://www.sjgames.com/gurps/faq/FAQ4-3.html#SS3.2.7
Partial Morphing is no longer part of 4E. You need to buy another "partially-morphed" template to represent the intermediate state of morphing.
Another consideration is to use a Modular Ability pool which may only be used to gain traits possessed by one of the character's Alternate Forms, or the Improvised Forms enhancement from GURPS Powers, page 75.
Category:Rules