shipping: tangible vs. downloadable products

[gourmetdelights]

Our store http://www.castlewellgames.com/index.html has BOTH tangible products (books), and downloadable products (PDFs).

The shipping options are 2:
A. Download via your email receipt $0.00
B. BOOKS: USPS PRIORITY MAIL $6.45

The default is option A since the majority of our products are downloadable games, AND the fact that many customers "are not readers" and thus having DOWNLOAD on their email receipt has saved us a lot of hassles (I never got my game in the mail. We're sorry, but it is a downloadable PDF, we just resent you the keys. Oh I didn't realize that. No worries, have a good day.)

HOWEVER the issue is, some people who choose the physical book, also choose the $0.00 shipping option.

Ideally we'd like to have it such that if someone puts a book in their cart the default changes to B for $6.45 OR in a perfect world we hope that option A disappears as an option. This happens with "FREE Shipping" that appears when the order qualifies, and disappears when the criteria aren't met, so I'm hoping we can do that with other shipping options.

I tried playing with "Flat base Each Shipping", setting the Downloadable products to "No Shipping Charges", with just one shipping option, but the problem is we DO LIKE having the "Download via your email receipt $0.00" reminder printed on their receipt so they know to download PDFs. If they only choose download games, they don't see ANY shipping options.


Thoughts?

Thanks.

[gourmetdelights]

I will note that I just changed the Default Selected Shipping Option to 'none' ( Commerce Setup >>> Shipping) which should help but being able to get a "Default option" as I described would be ideal....