I found these latex tensioners that are marketed for salmon fishing, yet work well for tensioning your tarps, tent fly, or hammock body (on some models).
For those of us that dont want to fuss with DIY, these are a relativley cheap alternative and can be purchased from Cabela's and Bass PRO Shops (possibly others). I have been using them for about a year without failure. Comes in 2 sizes also. Search sites for "dipsy diver snubber".

oooohhh, aahhhh, pretty colors