Mac,
Here's another idea - don't know if it would work but might be worth a try....
The swim platform on the ranger is slotted. I wonder if you could fashion a couple of sturdy boards with a wide section and handle at the top but just small enough to drop into the slots from above. Kind of like dagger boards but since they would be perpendicular to the direction of travel, they would just add drag. If it works, you could even adjust the drag by putting a few holes in the boards that would allow you to raise or lower them to predefined stops - e.g. a couple of cotter pins or dowels could be inserted to adjust the height.
Here's another idea - don't know if it would work but might be worth a try....
The swim platform on the ranger is slotted. I wonder if you could fashion a couple of sturdy boards with a wide section and handle at the top but just small enough to drop into the slots from above. Kind of like dagger boards but since they would be perpendicular to the direction of travel, they would just add drag. If it works, you could even adjust the drag by putting a few holes in the boards that would allow you to raise or lower them to predefined stops - e.g. a couple of cotter pins or dowels could be inserted to adjust the height.