Nuru, The King Kutter "sub soiler" tooth is a rectangular piece of steel inclined at quite an angle. Sounds a bit like your single ripper thingy but can't go nearly so deep. Sure 2 or 3 passes with a fair priced tool with other uses beats the pajamas off of renting a machine. At the time I rented my overnighter I didn't have the sub soiler or middle buster. I hope to be able to find or evolve a design expressly for laying wire, similar to the vibrating thing the contractors use to lay phone cable to houses. Given that a tractor has way more power to the ground than the vibrating cable layer, maybe I won't need the vibration.
How much does that single shank ripper cost? Maybe I could adapt it to lay wire.
When I was trenching in the underground electrical, gas, alarm, and water for my mom's house I used the FEL and got ditches 24 inches deep 24 inches wide, real steep on the side near the tractor and a little less so on the other side. Luckily the ground was near optimum for digging, not too wet not too dry. Can't depend on that!
Good luck to you with your trenching,
Patrick