Jim:
Glad to hear you are using the plastic sails as a former only, as they are never worth trying to put on the model.
My own view (and it is only that) is that unless you are modelling a ship at sea then a full suit of sails set on a static model just does not look right.
Jake is right when he says that a ship at anchor would unbend the sails, so showing a ship without them is certainly correct. This also eliminates a good part of the running rigging so for someone not experienced at this type of modelling it would be a good way to start.
If you are furling sails don't forget that the clews of the sail (the bottom corners eh?) were drawn in towards the mast and not straight up to the yard, resulting in a sailcloth bundle that tapers out from the mast to the yard arm. Furled sails also need all their rigging. In order to keep the correct perspective you do not make your furled sail full height, rather 1/2 to 2/3 is all that is required to achieve the correct size of furl. This is because the thickness of your sail cloth material will not be in scale.
A compromise option, and one that I like to use, is to brail the sails; this means to use the clew lines, leech lines and bunt lines to draw the sails up to the yard but not furl them. The sail hangs down like a bag. This is the way sails appeared just before they were set or furled, like when getting ready to depart or anchor. This allows you to display all your sail and rigging handiwork without detracting from the details on the decks.
You can also correctly mix these options, furling the upper sails, setting the top sails, and brailing the courses for example.
Don't forget that you can also brace the yards around for a more interesting and accurate working appearance. Yards were rarely if ever squared up when the vessel was working.
For information on sail making try "Historic Ship Models" by Wolfram zu Mondfeld, or "Ship Modelling from Scratch" by Edwin Leaf. Both discuss the issue of sail sets and their manufacture.
Remember that a quick look at any collection of models will show you that sails are displayed in all possible sets. At the end of the day it is your model and so whatever you decide to give you satisfaction will be correct for you and your model.
Good luck and feel free to come back with more questions.
Bruce
PS:
Hear you bought a spokeshave ...