I recommend you try gaffer tape instead of duct tape.

Advantages:

• Remains flexible and removable forever.
• Looks nicer, a cool matte black or manynother colors.

Where I get off making this recommendation:

I needed a light-excluding bellows for a photographic project. I made one using black illustration stock and gaffer tape. It worked extremely well on the first version and held up to hundreds of cycles of extension/compression. My application was sensitive to pinhole light leakage and there was none.

It would have lasted longer but that was the end of that project.

My two cents. I love DIY stuff!