I use both base shaper and an organizer, all purchased from PurseBling. Doesn't add much weight and the structure of the bag looks great, and it's so nice to be able to find things in a split second!I have a Speedy 35 and use both. I purchased all my base shapers from eBay, dr.baseshaper is the seller I purchase from.
I have a 25 and love my organizer from Etsy shop Divide and Conquer. It also serves as a shaper.
I would just use an organizer. Some members on here have expressed concern that a base shaper can hurt the corners of the bag.