What to do with SilPoly

Unfortunately my last order from RSBTR was damaged in transit and my membrane silpoly had a small hole in it about 15cm in from the edge.
As it is for a tarp and I'd have to trim both sides to centre the ridgeline I would lose about 30cm width which doesn't work. RSBTR have been kind enough to replace the damages piece which means I now have 4 yards of 15cm narrower silpoly to play with.
I was thinking of making a silpoly bathtub floor and Tyvek topped s/bag cover to offer some protection when tarp camping but before I go chopping up a great piece of fabric I thought I'd ask for ideas.
I did think about a waterproof outer synthetic quilt but am worried that would just trap sweat and body moisture in reality.
Or, maybe an all silpoly bivy bag for trips where I plan to make a hut (NZ) but for whatever reason have an unplanned night out.
Or, a mini tarp ~1.8 X 1.2 made to use as a vestibule extension for my Lanshan 1 or 2.
What ideas do you folks have?
As it is for a tarp and I'd have to trim both sides to centre the ridgeline I would lose about 30cm width which doesn't work. RSBTR have been kind enough to replace the damages piece which means I now have 4 yards of 15cm narrower silpoly to play with.
I was thinking of making a silpoly bathtub floor and Tyvek topped s/bag cover to offer some protection when tarp camping but before I go chopping up a great piece of fabric I thought I'd ask for ideas.
I did think about a waterproof outer synthetic quilt but am worried that would just trap sweat and body moisture in reality.
Or, maybe an all silpoly bivy bag for trips where I plan to make a hut (NZ) but for whatever reason have an unplanned night out.
Or, a mini tarp ~1.8 X 1.2 made to use as a vestibule extension for my Lanshan 1 or 2.
What ideas do you folks have?