Extra Shafts for Eclipse Blankets?

I am trying to make a draft in summer and winter for the picture above.  This is a photo of the cement floor under the grape-arbor pergolla that we were watching the eclipse from.  The spaces between the grape leaves are being camera obscura and showing the progress of the eclipse on the floor.  I have 16 shafts to work with  (I thought getting the AVL would cure shaft envy, but NOOOO).  I am going to manipulate the image to try and make fewer blocks in the design, but even so, I don't think I can do this with 16 shafts (14 blocks).   I have considered adding a few temporary shafts (wooden sticks with strings tied the appropriate warps).  Has anyone ever tried anything like this, or have any other suggestions. I want to weave four large cotton blankets in this pattern, so pickup isn't an option.