I've tried everything under the sun to mount a GPS in that position. The whole "nose" of the bike is simply not ridged enough. The vibration on dirt roads destroyed my GPS 2720 while in Alaska. Even a wash board tar road had way too much vibration.
I finally took a piece of 3/16 X 2" steel, bent it to the shape I needed and bolted it to the handle bars. On all my bikes, I've found the handlebars to have the least vibration, and the most easily reached location for a GPS.
2007 Suzuki DL650 V Strom abs
2007 BMW K1200R Sport abs
2004 Honda VFR abs
2001 Moto Guzzi Rosso Mandello