4000' runway in a GV is suicide??
I used to operate a GV out of EGTK, Oxford, England. Its about 4300'. Hardly even touched the brakes on that runway.
I think you have mixed the numbers for a G4 in there. 4000' would be tight for the 4, yet doable.
The Vref for a G5 is much lower than 129 at typical landing weights. I seem to recall 108.