That's going to depend on how you load the trailer. As I understand it, you want 10-15% of the total trailer weight on the tongue. Putting stuff close to the front of the trailer increases tongue weight. Putting stuff behind the axle decreases tongue weight.
Lessee - the 19' has a dry weight of 2600 pounds.
The combined volume of the grey and black water tanks is 40 gallons - 350 pounds. (I don't know how far forward the tanks are mounted.)
Assume your fresh tank is empty.
You might have 40 pounds of propane.
We have just hit 3000 pounds. You need to keep the rest - pots, clothes, luggage, food - under 500 pounds.
A weight-distributing hitch adds weight too - and totally messes up the tongue weight concept. Also, I don't know if the battery is included in the dry weight.
Also, you need to understand all the allowed weights. When your trailer is fully loaded, you probably cannot carry as much stuff in the Explorer as you can when not towing. An excellent resource is the Trailer Life Towing Guide - http://www.trailerlife.com/SharedCod...cfm?id=2085931
A discussion that won't answer your question but which should give you some insight is at http://www.fiberglassrv.com/board/in...howtopic=33912
A Toyota document that explains all of this is at http://mediap04.toyota.ca/media/pdf/...ng_guide_e.pdf
on the second page.