Billman--I hate to suggest that any job is not perfect for a new tractor, but I think using a middlebuster or other 3. attachment (except maybe for Hoghead's custom wire-dropper) will create a lot of unnecessary mess. Invisible Fence wire only needs to be down about 3-4"--much more and it loses effectiveness (in fact, it works best if it's not buried at all; in our woods, we just lay it under the branches and bushes). I've rented a gas-powered slit-trencher for, say, $55 a day that opens a slit, lays the wire, and closes up the slit, and we did about 5 acres with IF in a day. The machine was not self propelled, so the hills were a pain, but the result was much neater than the furrow from a sodbuster. As to "do they work," you mention a puppy; I think about five months is the earliest you can expect good results training to an IF (and I agree with Richard; you have to really pay attention to the training so it's clear to the dog what the rules are). we have had exceptionally good results using IF to contain our Australian Shepherds. It seems to depend some on the breeds; roaming dogs will test it, while territorial working dogs, I think, like having firm boundaries they can patrol and enforce. And some of 'em are just dumber than others; we had a neighbor who had an Airedale that appeared to love the stimulus provided by the shock and would just stand by the antenna quivering with the "thrill" of it! /w3tcompact/icons/laugh.gif
Rick