I would leave the seats in there, and not worry so much about the extra 135 pounds.
That said, if you really want them out, Honda does sell a 1" thick book that covers anything you might possibly want to do with one.
Make sure that you stay away from any yellow wires. They are yellow to keep mechanics aware it is part of the air bag wiring. Cut it or apply 12 volts to it might cause the air bags to deploy or not work correctly. You might have seat belt tensioners that run on 12 volts. During a crash, they tighten the seat belts to secure the passengers better.
Good luck,
Fred.
