[hagcam]

Last year I changed my microphor toilet to an RV drop toilet. One of the best changes I ever made. My old toilet worked okay, sometimes I would have to use the handle twice to get the toilet to flush. I didn't like that it used almost 2 litres of water every time it was flushed which wasn't a problem most of the time except when boon docking, the black tank would fill up first.

I drilled through the floor, (3/4" plywood, and sheet steel), then through the top of the bay (steel) and then into the plastic tank. I used 3' pipe, and the hole in the tank was slightly offset to the toilet hole. I used 2 45 degree elbows. It has worked without a problem. I think that it would not be a problem if they don't line up perfectly. In house plumbing I think they put a 1/4" drop per foot. Even two 90 degree elbows would not be a problem. I your bus, I would recommend expanding the existing hole in the tank.
I used a grommet, like this one, for going into the plastic tank.

http://www.ebay.com/itm/RV-Dump-Holding-...2c83fc7830


Removing the Microphor toilet also got rid of the 12v compressor, which I removed. That gets rid of the 12v draw when boon docking. I also was able to move the toilet 8" back because there is not the tank on the new toilet, more leg room in the bathroom.

All in all a very good upgrade, downgrading my toilet