Do you want us to keep our comments and questions out of your sail making thread? If so, I'll ask here... what type of sewing machine are you going to use? Will it require a heavy duty one or will you be able to roll the sail up and feed it through a regular one?
Looks good BTW
Shhhh!dont call me that, those fellas have spent years perfecting their art . some of the more modern versions have lofts full of computer driven cutters that even go BING and flash lights at you. 
I am sure that an idea chiseled onto the floor of cave will never be the same.
Meanwhile the machine I'm using is a Singer 20U industrial which does a nice zig zag, needles are 130 guage (denim is usually 90), thread is no 36 polycotton.
You have to be really careful when sewing monofilm.but I tested the polyethlyene and comfortably sewed 8 layers. the sail has 7.
The sewing table has slowly got bigger as I scrounge more good sheets of chipboard, and is becoming a problem ,because I want to slide a 16' hull into the shed to restore and convert it to a minicriuser.
Darn nice looking effort on sail Paul.
Can you show a picture of your sewing machine? (I didn't take notice when I was there last.)
Cheers, Bill
Paul .. I did a sail once from some Dark Green poly tarp (stronger than the common blue stuff) ....about 4sqm it worked well for a few days untill a super hot day. The sun heated up the sail and delaminated it.
The material that you have got is much better...Good luck
I once saw a sail maker use "double sided tape" to stick an entire sail together to get the shape right before it went to the sewing machine.
That way the machinist could rapidly sew the seams... seemed to work well.
I have just checked my windsurfer sail ..it looks like it was done the same way as you can see the tape in the joins.
The tape would be about 8mm wide.
If thats the same stuff I got from the kite shop to make RC yacht sails, it gets stronger the longer its left in the sun and from memory (don't quote me on this though 
) you don't need to sew over it. Probably different for sails though as I guess they'd be under significantly more stress.
I use miles of the stuff! At bunnings they had scotch brand at $8 for 3m. At crazy clarks it was in 10m rolls for $2. these were 50mm wide rolls so I cut it length ways with a stanley knife into thinner strips of 15 or 25 mm . thats 40m for $2
last time I went to buy some the 50mm rolls were gone and they only had 25mm rolls so I bought every roll in the shop!. That is what Im using on the current sail,as the seams are mostly 20mm. the thinner strips are mainly used for batten pockets.
An alternative system is to hold the panels together with packaging tape ,preferably clear and sew straight over it, then peel off afterwards. this system actually works really well,but on really old sailcloth you sometimes get little bits sticking too well to the mylar surface .
Alternative 3 is to use contact adhesive to glue it together then sew later. that works too and I used it to make Gaff sails for my schooner.
I spent a night on the internet , all to no avail. I suppose youd have to ask a sailmaker. The small roll I have was bought from a Kiteboarder in Falcon who had been making his own sails,then disovered the joys of teabagging and stopped making his own sails. The roll ,of unknown length was getting quite small but would only be parted with at a relatively high cost to me . I 'm sure I still got a bargai
I may yet be sniffing around his stockpile.
If someone does find a reasonable cost supply , let us know , we may be able to do a joint purchase and divvy up later. 4-5 OZ cloth would be great
