i was just theoretically wondering if you could call this a 512bit encryption ?
you "split" the file into 2 channels of 128bit block and interleave them into a 2 encrypters with different encryption keys.
so that AES take 1st,3rd,5th ... block
and serpents takes 2nd,4th,6th.... block
both the encryption keys will be derived from the same password but with different hashing methods and different salt.