Duct Tape Binding
Well, it has already paid off ! Check this out : Steampunk Album and How to Make a Binding Using Duct Tape. The YouTube video is almost 15 minutes long! I fast forwarded it to about half-way (where the actual construction begins) and was immediately ecstatic (ecstatic shock ?) over the technique.
How about a wider gap with parallel vertical strips of bookboard to make something that looks like this Curved Spine Binder ?
I should be able to try this out fairly quickly. I found a Utrecht Art Supplies shop within walking distance of my work. They sell huge sheets of board -- everything from thin chipboard up through heavy Davey Board which is usually acid-free). And they have a monstrous self-service chopper in the store you can use after you pay.