I have my main on slugs and a 10 year old could jump the sail. Here are the must do's:
1. Have the right size and type of slugs - well coated with sailcoat. (I will try and take a picture of mine)
2. Free running sheaves at the mast head
3. Flake the sail EXACTLY the same way each time - I start to port and then alternate each flake. The slugs get orientated to flake to one side - if you try and flake the other way the slug will create a lot of friction.
David