Help with heat exchanger

Looking to build a stand alone heat exchanger to run a herms coil. I'm looking for a little guidance on doing it right. My plan so far is to use my old 5 gallon stainless pot, with a 3/8 copper coil, and a water heater element. My plan so far is to use this controller: http://www.coleparmer.com/catalog/product_view.asp?sku=9352002 and an element similar to this: http://www.plumbingsupply.com/images/water-heater-element-02203.jpg I have a couple of questions. Do water heater elements have to mounted horizontally? Am I going to need an ssr? Source? Should I go with a pressure cooker rather than a regular pot?

How about using a corny keg? It will hold pressure.

Have you seen this yet?
http://sdcollins.home.mindspring.com/HX.html