I inherited a sweeper and had not really liked having to take all the extra time it took to make the second trip over, so rarely did so. Then I saw one advertised that had an offset tongue. That was what I needed!
I decided to retrofit my rigid tongue AgriFav model to be offset.
6-8' of 3/4" EMT galvanized conduit
3 each clamps; I used U clamps, but imagine hose clamps would work fine
Hammer, a ball or sledge
1/2 inch bit
Wrench, pliers, screwdriver to tighten clamps
Grinder or file
Step 1: Adapt Conduit to Be a "Tongue"
I then used my drill press to drill a hole in the end. I did some pretty intense measuring (at least by my standards) to get the hole in the exact center. I even used a punch to set a dimple for the start. I slid into my home-made drill press rig (maybe a future Instructable) and used a step bit to drill the hole. I matched the hole size to the hitch pin I use.
I have found that a tongue with rounded corners works better on a tight lawnmower drawbar, believe me, so I used the angle grinder to round the corners, and smooth the hole edges.
Step 2: Fit the New Offset Tongue
Step 3: All DONE!
I learned the hard way that this thing works better in dry grass than grass with dew on it. I usually cut mornings instead of afternoons, but will have to change to make this system work.