I'm interested in not long-term storage but how to best display a book for SHORT-TERM storage and for resale.
A problem at conventions is pulling a book in and out of its bag repeatedly for potential buyers to look at. This may be a good idea for high value books but for books less than $100, it's frequently not necessary.
If you can clearly see the back cover through Lexan, but have the rigidity of a fullback (which is only 42 mil vs the 60 mil we're talking about with Lexan), that would potentially be a good way to display and protect rack books.