It works like a charm in all moist loam soils-with the heavy model Burkeen put out years ago 10 inches is no issue. You could even have a metal shop make one. With the right moisture works to 6+ inches in clays to sands. Been using the tool more than 35 years and the speed coupled with rapid backfill that leaves almost no marks it can't be beat. The only impediments are large rocks and thick roots.i can honestly say I have NEVER used that to install irrigation pipe.
how could you possibly install the lateral deep enough using that method?
Are you installing is pure peat? or possibly marshmallow?