I will be transiting FRA, TXL, and MUC on an upcoming trip (routing is IAH-FRA-TXL/NUE-MUC-ORD) and was wondering where the best place for me to visit a WorldShop would be. I have a few hours in FRA before heading to TXL. My return connection at MUC is just over 1.5 hours. I'd like to be able to submit the VAT forms if possible. Is my best bet to buy at FRA and submit the forms at MUC?