Decided to cheese-grater my seat. Did this to my last bike, never had a problem with water ingress or the seat base breaking or anything! 15 minutes with a 10mm drill bit, stripped another 150g off the weight of the bike. You'd have to spend $800 on titanium bolts to get the same weight loss, or take a big dump on the toilet before you go for a ride. Maybe do this to your seat, AND take a dump?
All I need now is some nicer looking bolts!