The brightness dropoff will be significant. Calculator says 100" gives you 16.5 ftL on low. Going up to 130" brings you down to 9.9 ftL, and 140" gives you 8.5". Then you have to factor in the drop due to the gain of the SF (not sure what it is) being more than the spandex.
So you could be looking at half the brightness you are getting now, or even less. For comparison, on your 100" screen, going from high lamp to low lamp is only a brightness difference of 23% or so.