Spritcha, another easy way to test tension for bigger guys or those who cbf'd is to buy a luggage scale. Most have a digital readout on the top of the handle so they give you specific readings. Cost is about $15-$20 for a 50kg capacity, more expensive for higher capacities (up to 200kg).
[ame="http://youtu.be/ZlVpszQuTfQ"]SuperTraining.TV: Stand on the Band Deadlifts | How To - YouTube[/ame]
For me personally, I'm 5'10 conventional pull, when using the "Stand on Band' approach for deadlifts, bands give the following tensions:
Band type: tension at bottom kg/ tension at top kg
Mini Band (red): 0kg/20kg
Small Band(orange): 0kg/30kg
Light band (purple): 0kg/45kg
When using band-resisted movements starting out with a 10% tension is a good place to start, for band assisted movements (reverse band work) 10-20% would be my suggestion.