Is the Dufour 28 a mast head or fractional rig?
If it is a mast head rig, the baby stay can be used to bend the mast, thus depowering the main.
Babystays are also used to prevent the mast from pumping.
Why does he want to install a self-tacking jib?
ISPA Yachtmaster Offshore Instructor Evaluator
Sail Canada Advanced Cruising Instructor
IYT Yachtmaster Coastal Instructor
ASA 201, 203, 204, 205, 206, 214
As I sail, I praise God, and care not. (Luke Foxe)