I've ordered some acrylic pearloid replacement tuner buttons from Taiwan. Hopefully the reduce it sufficiently so that I don't have to do much in terms of counterweights, but the neck dive is very noticeable at the moment ...
As you can see in the listing they are the same shape as the Grovers
http://www.ebay.com.au/itm/like/160947193050They accepted my offer of $9

EDIT: The buttons arrived today, and were easy to fit and reduce the weight by a considerable margin, almost eliminating neck dive. The difference between these self-locking Grovers with acrylic buttons and the Gibson tuners is now not much at all.