OmnSaft adds full-screen browsing feature to OmniWeb. It is free-ware for private uses. Go to download page to grab your own copy! OmniSaft works only with Mac OS 10.3.4 and OmniWeb 4.5 (v496).
Please read the README file about how to install and use!

You can go to my software page at Kagi directly here, and choose Saft Donation (since OmniSaft is still Saft) to make a donation, two donations or each commercial usage.