True Solar Sails

[J.]

For making speed depend on the number of stars in the system, would this work:

Make the solar sails give triple the movement, like 18 instead of 6 for example. Also increase the supply storage, but only make them generate enough supplies for 6 points of movement to be possible. This way, when you have a system with three stars, the ship would generate three times the supplies and could use all the 18 points of movement.

Or, is there a problem with this theory?