What you did is OK however I would have used a mechanical coupling on "no hub" coupling to transition from ABS to PVC. I never trust the various transition glues, the joints all seem to eventually loosen and leak. The mechanical joint will not fail. Rolling up the 45º to create more fall isn't quite kosher either, but in your RV application I guess it maybe OK.
Rolling the pipe creates a trapped section of pipe that will always hold water and potentially collect debris and create a clog.
In your RV application you maybe able to get away with it because the RV is moving enough that holding water may not matter.
I like the idea, hopefully it works out for you.
No hub coupling