The way I understand it is, when you are hooked up to a 50 amp service and split it into two seperate feeds, you have two 110 volt, 50 amp lines. Each 110 hot leg of the 50 amp service is 50 amps, not two 25 amp legs.
The side that is feeding the main shore line is going through your circuite box in the MH. It should be OK. But if the one that feeds the rear AC unit is not going through a breaker, like mine is not, then you are feeding up to 50 amps of power directly into an appliance that should not use near that much. If something goes wrong there is no 20 amp breaker to protect it. 50 amps could do a lot of damage before tripping the breaker.
I made the short 'dog bone' (50 amp male to two 30 amp females) that I use when I need it, but I get worried when I think about it.
I have intentions of making a short 10 foot long extention that plugs into a 50 amp service and terminates with an outdoor type breaker box containing two 30 amp breakers each with a 30 amp outlet. That would give lots of flexability without a lot of bucks.
'Can't never did nothin'!' - My Dad