This is the bathtub mod I have now done on two Scamp 16's.  The following is for the new trailer, a 2013 Scamp 16. I took out the front couch and then did the mod as shown.  I had done exactly the same thing on our 1999 Scamp 16--same layout.

Our old Scamp was totaled September of 2012. We were crossing the bridge on I-94 to go in to Minnesota (minutes from our campground), and I slowed for a truck ahead of us.  The delivery van behind us didn't.  He totaled his van, our camper and the front of our camper jumped the hitch and damaged the back of our Explorer.  We had to wait 18 days for our SUV to be fixed.  The only good thing was we weren't hurt.

The reason for the bathtub--Judy hates showers. So, while I head out in the weather to go to the showers, she can soak in the tub with her candles, bubble bath and soft music in the background. 

When we arrived in Sebring for our first outing with the tub, apparently the word had gotten out, because there was a long line of people waiting to see it.  Lots of envy from the wives.  The men were thinking, "Oh, crap."

As far as the drain is concerned, I have a hose fitting and the hose drains it out.  As far as the water, Judy fills her dishpan and dumps it in.  The gas water heater in the old camper had just enough hot water; we have the electric/gas water heater in this one, and using it on the electric mode provides more than needed.  Since we have no black water, we drain everything with two hoses.  WalMart has the graywater tank adapter for a garden hose.  Works for us!  (We only camp with full hookups.  If no sewer, we use the blue containers to haul gray water away.)

Enjoy the buildout!

Framing and cutting the drain hole. Notice the board on the back is narrow to allow the tub to fit closer to the wall.

The tub is in, dimensions are 46" x 24"--48" would have been a problem.  I got the tub from RV Parts Country on the internet.  $183.55 including shipping.

Framing the front couch. Most of the framing was with 2 x 2's.

And the finished product.  Just need a Rubber Ducky and some Bubbles!