Have you been using Impossible's new PX Shade? It's a very cool, affordable light shield for SX-70 and SLR-680 folding SLRs that protects the frame from exposure when it is ejected from the camera. If you haven't looked at it yet, here's the link to the item in the Impossible shop.

http://shop.the-impossible-project.com/shop/accessories/ac_px_shade

I can say after having used it, it works flawlessly, and it does a fine job protecting the frame from light when the print is ejected. But inserting or removing the PX Shade from the camera became a bit of a challenge. The PX Shade is made of thin mylar membrane that has a metal strip along its leading edge which serves as a weight so that the PX Shade is always angled downward. As a new photo is ejected from the camera, this design ensures that the PX Shade is in direct contact frame as it is being ejected, preventing any light from reaching the developing image. However, owing to its lightweight mylar construction and the metal edge, the PX Shade flexes so much when you are inserting it into the camera that it can be difficult to install. And when you try to remove the PX Shade by opening the film door and pulling it back out, it's difficult to get the the metal strip to go back inside past the film door's ejection slot.

The quick and easy solution is to use two dark slides for installation and removal. To install the PX Shade in your SX-70 or SLR-680:

1. Take two dark slides and sandwich the PX Shade between them, aligning the leading edges of the dark slides with the metal strip of the PX Shade.
2. Open the film door of your SX-70 or SLR-680, and insert the PX Shade sandwich over the rollers, but under the film door flap.
3. Gently push the sandwich forward until the PX Shade sandwich slides through the ejection port of the film door.
4. Pull the dark slides out and position the PX Shade in its forward, installed position

Removing the PX Shade from the camera also can be perplexing. Owing to the metal strip on the leading edge, the PX Shade cannot be easily pulled back out of the camera. The solution is to use the two dark slides again. With the PX Shade installed in the film door's ejection slot, proceed as follow:

1. Open the front film door of the SX-70 or SLR-680 folding SLR
2. Pull the rear edge of the PX Shade back about one inch
3. Position a dark slide over the top of the PX Shade and gently push the dark slide forward until it extends thru the frame ejection slot of the film door.
4. Position a second dark slide under the PX Shade and gently push the dark slide forward until it extends thru the frame ejection slot of the film door. 
5. Position the PX Shade's metal leading edge so that it is between the two dark slides.
6. Grasp the rear edge of the PX Shade, and pull it back carefully until the metal strip slides back past the ejection slot of the film door.

At this point, the PX Shade and the two dark slides can be removed from the film door. You can now use the PX Shade in another folding SLR model.

I've uploaded a video that I hope will help demonstrate how to use dark slides to easily install or remove the PX Shade.