Nowadays all Minis have the more or less the same sail wardrobe which contains one Code Zero (historically called Gennaker “Genak” by the french) which is used for going upwind in light winds and for reaching.
The rule of thumb for the Code 0 (a FR0 if for the experts) is that it should have roughly the same size as the main sail, so about 30sqm and it is being used on a furler.
One problem of furling sails though is that they tend to unfurl themselves when being set because there are no sheets wrapped around it.
The mini sailors have a simple trick for that: Velcro tape
The sailmaker sews 2-3 stripes around the clew: one side vertically, horizontally on the other.
Now when the sail is being furled it is sticks to itself which is holds up surprisingly well: even in choppy conditions going upwind the sail does not unfurl itself.
To unfurl it you simply pull the sheet and the velcro will give way.
This post is also available in: German