iFly Streets is tied to the SD card for licensing reasons. We co-developed iFly Streets and we cannot allow it to be duplicated from card to card, under our agreement. This is the only way the third-party would agree to it.
In most cases, the 8gb card should be just fine on space, but for those that is it not, just have a larger 32gb card for aviation and use the 8gb Streets card for streets. Maybe just keep it in your flight bag... It's not possible to run both at the same time, just a swap and your ready to drive. This is how many of the dedicated devices like AvMap, BK and Lowrance handle it. Thanks for your understanding.