I took a length of 4" Sch 40 PVC tubing, 2 clean out adapters with threads, and 2 threaded caps. I cut the 4" PVC to fit where the adapters extended outside the sides of the trailer on each side. A friend of mine painted his International Orange so he could see them when he was backing for guides. I left mine white. Under my 3400 the cover on the bottom is held on with threaded bolts. My dealer took some plumber's tape (metal strip with holes in it) cut a length that would fit around the PVC and then bolt to the frame using the bolts for the undercovering.
I drilled a hole in the top and bottom wall of the PVC and took a 6" long, 1/4" bolt with washers and nut, inserted it thru the holes to make a stop for the sewer hoses. I have a 20' hose in the left side and a 10' on the right side. I will post a picture later if someone is interested..
BC