Adding a forwarding message would certainly be a good move, and would help with the Page Rank of the new site. The Google people can't/won't do anything here.
If anyone who has links to the old Geocities address changes them to the new formula 16 site address, this will help promote the new site over the old site in Google's mind.
One such place is the welcome message in this forum - Wouter, could you edit that post?
