at very least, if you really want to waste that amount of cable, place some cap close of the LCD VDD/GND (47uF (or greater) + 10 uF tantalum and finally 0.1 uF ceramic)

I don't think there's a real problem with the length of cable so far, my feeling is that you just need to filter the Vdd rail properly at the end and probably play with COMMANDUS & DATAUS DEFINEs.