For modest-sized paddocks (like not more than 200' square, ish) honestly I have to admit I do not use proper tensioners (although I am certainly in favor of them!).
Instead I take the cheap/quick/dirty/lazyish approach of having each inside corner insulator held to the post by baler twine (the hi-test thick synthetic stuff that comes on the 650-lb big sq bales I get). YOu wrap the wire *twice* around the donut-style corner insulator, then thread the baler twine thru the donut hole, tie an overhand knot, and then knot the twine again around the back of the fencepost. The key is to make it LONG, so that when the fence is under tension the corner insulator is out at least 8" from the post. (Try it and you will see what I mean).
To retension the strand, all you have to do is go to one or more corners, untie the baler twine and retie it tighter. (That is the reason for having it so far from the post -- to give you room to snug it up later!)
I also find that the built-in slight elasticity of the baler twine helps absorb seasonal change in wire length, and while I have had metal wires break on "properly" set up fences on occasion (like when it gets down to -30's C), I have yet to have it break with the baler twine corners.
Again, not knocking the storeboughten tensioners, and really on the whole they are probably a better arrangement -- but the above demonstrates you can get along pretty well without them if you prefer, too.
Pat
