I just finished an UQ made of the JCP jackets. Used 2 3XLT jackets following the basic layout others have used. I sewed & cut rather than seam ripping. Used all but the 2 front panels and the arms (to be used for items).
I use 3 small dart on each long side. 1/8" shockcord suspension (15') using a cordlock to join the ends to enable shortening if needed. Used 1/8" shock cord on the ends, sewn in on one side and a cordloc on the other to draw up. 1 1/2" grosgrain was used for the shock cord. I did not run a continuous piece of ribbon down the long sides. I split it into 4 sections so I could add/change darts and use hangers if needed.
If memory serves correct, I ended up with 60" x 40", for a nice spring/fall 3/4 length UQ.
What worked well:
1) The darts really seemed to make a difference
2) Shock cord suspension
3) Sewing & cutting seemed to be a big time saver
What I would change:
1) Use the sleeves at the corners rather than piecing in other smaller bits
2) Use 14 or 14.5' of shock cord (for my WBBB)
Here's what all I remember using (approximately on some things)
2 3XLT jackets
1 spool polyester thread (125 yd)
1 roll of 1.5" grosgrain ribbon (25')
20' shock cord
In the stuff sack I ended up with 17 oz.