I have a question about MMTK. I want my GC Header to be 4 words size. I see the change in the size of each object allocation that 4 words are allocated for GC Header but I cannot mutate those words. The method prepareavailableword() , readavailableword(), writeavailableword() works only  on one word in GCHeader. How do I read and write this 4 word sized GC Header? 

Hari Krishnan