Well, I've finally completed running my entire mame 0.80 rom set through zipmax.

I've managed to shave off 85,663,438 bytes (81.7 megabytes) by using a combination of 7Zip, BJWFlate, and DeflOpt. I used other zip programs as well but I don't think any of them were able to improve on 7Zip + BJWFlate.

It only took about 19 days on my P4 3GHz. Obviously the time spent was excessive for the return that I got but I just wanted to see what I could do. Also, in the future, I'll only have to compress new roms that I add top my collection.

The only odd thing I encountered was that BJWFlate had an error compressing the Sport Fishing 2 (sfish2) rom set.