I just traded my (3rd) Gen 3 Prius for a new Sienna. I built and used a sleeping/storage platform for the last 2 years, and I'm offering it for sale for $400. The price includes a full width setup, 40% width, 2 mattresses (1 for each width), and help with installation. The build quality is not super high, think of it as a prototype, it works extremely well but wasn't built to be pretty. It doesn't look bad either, especially if you have a gray interior. It looks pretty good for all of the use it got. Installation requires removal of the rear seat and a slight modification to the center console lid, which can still function normally as needed. I'm in the Orlando FL area. I can travel to deliver for the IRS mileage reimbursement rate for the round trip. I have it on Marketplace: https://www.facebook.com/share/SoRovMaTYSDt2wXz/ Here's a video:
