Finally found a killer deal on this after looking for about 100 years. Now, If I was to use the Fuji FP-3000B film in the back, Can I remove the pack half way thru and insert for example my pack of FP-100B? Also, I understand they make a 120 film roll back for this that can be switched to 6x6, 6x7 and 6x9. Is that really correct. If so, that's pretty nifty. Thanks for any help.