Planning to ride the Trans Taiga road this summer on my R1200GS on Heidenaeu K60's. The road is mostly loose gravel with some larger, sharp rocks at the end. The area is VERY remote and has no services. I have alloy rims which do not allow me to use a tube in the case of a puncture. How low can I drop the tire pressure to improve handling before I start in increase the risk of flats?