I'm a sailmaker, and the first question I ask when I visit any competitor's website is "what cloth are they using for this sail?"
For those of you who would like to see what Challenge Sailcloth offers in its range of woven dacron sailcloth, go to challengesailcloth dot com and follow the links to their sailmaker pages. You can download specification sheets for every dacron cloth Challenge sells in the 6, 7, and 8 oz range to see the actual weights of the dacron.
At the same website, there is a link to Challenge's Application Guideline chart showing what cloths are recommended by Challenge for use on different boats.
Take MedSailor's Formosa 41 as an example.
For cruisers, Challenge recommends using "9.18 Performance Cruise" or "8.88 High Mass" for the 100% jib
(aka #3 genoa). Cruiser/racers willing to pay a little more could choose the "8.63 High-Modulus, High-Aspect" dacron.
If the Formosa is a heavily ballasted boat sailing for its LOA, it would be prudent to select a cloth recommended for a 42-48' boat. In this case, the cruising cloth recommended by Challenge would be either "10.18 Performance Cruise" or "9.88 High Mass Dacron". Cruiser/racers willing to pay a little more could choose the "9.3 High-Modulus, High-Aspect" dacron.
some things that I noted:
#1 Precision's webpage for a Formosa 41 headsail specifies that they will build all the headsails for this boat using "7.6 oz. Premium Challenge Dacron". They use the same cloth for headsails from a 95% jib
(aka #3 genoa) to a 160% genoa (aka light #1 Genoa).
A sailmaker usually selects different cloths for a tall skinny jib
used in strong wind than s/he does for a short, wide genoa for use in a light breeze.
#2, Challenge doesn't make anything called "7.6 oz. Premium Challenge Dacron". Nor do they manufacture a dacron sailcloth that weighs 7.6 oz.
#3 Based on the limited information Precision provides on their website, I can't satisfactorily answer the question: "What sailcloth are they using to build this sail?"
[Full disclosure: My name is Judy Blumhorst, and I am an independent representative for Hyde Sails USA]