Assuming you are going to put the 790 rom into a 780, be sure you copy all of the bUseful backup files from the Windows folder first as the 790 rom attempts to install them into the flash memory, which will no longer be present, hence no backup program.
But you can copy the 780 files back onto your new hybrid afterwards and it works fine.
22-250...I own one with a 36X scope and bipod. Use it for shooting out headlights of cars a mile away....
Rich