I've got mine down low on the A pillar. Not blocking any of my vision but still technically able to be detected. BUT most cops (in my limited experience) are sensible and use common sense. I asked one I was doing some work for and he said he would only defect it if I was pulled over for being an idiot.
I might move my gauge down into the coin holder now. I only installed it after finding a MBC and wanting to know what the previous owner was running the boost at. I don't need to look at it all the time.
The gauge is in a legal position, but it may bring attention to the fact the car has a MBC, which although is relatively well hidden (in the ABS relay box) is still illegal.
I wouldn't worry. My gauge is connected to the A pillar, as a lot of other people, and never have problems. The only time you would have to remove it is if you get defected for something else.
^^
i was defected by Surry Hills police in NSW, who are known as one of the strictest, they both had a really good look inside the cabin and missed both my tint and (low as possible) on the a-pillar gauge..