Thanks for the replies. I checked out hexcel, and downloaded and read HexForce_Technical_Fabrics_Handbook.pdf. Page 30 title "Aerospace Carbon Fabric Construction Data", and page31 "Commercial Carbon Fabric Construction Data". The yarn used in aerospace section is "T300 3K", yarn in commericial section is "3K Carbon, 33MSI". What is the difference? Should we use aerospace grade only?

Aircraft Spruce supplies Style 284 bidirectional carbon 2/2 twill, 5.7 oz/SqYd. This product is in the above commerical section of Hexcel. So it seems Aircraft Spruce is supplying commerical grade for airplane homebuilders. Is this a problem?