I faced a similar problem but didn't want the cost and complexity of a 3rd party mount like RAM, etc.
Here's what I did to mount my netbook (Acer Aspire One) which is similar enough to your Asus...
That's a piece of 1/16" thick aluminum plate cut to fit & bent to the right shape. It's bolted in place using the existing bolt holes that the 3 gauge cluster uses. I used 2x 2x6" pieces of stick on velcro (rough side on plate & soft side on netbook) to secure the netbook to the plate.
I've had it on washboards, rock crawling, etc. and it hasn't complained a peep.
On freeways, it does occasionally vibrate reaching a resonant frequency but I simply push the lid towards the gauges and that stops any oscillations almost completely. It doesn't come back for at least 3-4 hrs so making it more secure versus doing that 2-3x a day on road trips was not worth it for me. Off road, this doesn't happen due to the irregularities in the terrain. Also since most of the weight in at the back, close to the attachment point, the whole unit doesn't vibrate like you would think it would.
I did have a backup plan if the vibrations were too much and that was to use a thicker piece of aluminum.
:sombrero:
HTH.