No. You'd just get less face level fresh air. You'd also have to make sure there's an air-tight seal behind the gauge(s). The cold/heat/moisture can wreck them.
Never been a keen on loads of gauges. If I ever want that much info, I'll probably get something electronic and incorporate everything.
:nod: I'd like to replace the A-pillar with a 2 bar. I originally got an A pillar boost gauge in the S14 cos I needed it for the mechanical boost valve I had. Then I got an AVC-R...then a Blitz TT. Never looked at it again. Thinking about it, maybe I should get something more useful for the A Pillar...
I only have a boost gauge at the moment, (only mod is manual boost controller). It sits under the dash near my left knee. I can only really see it if the wheel is straight which suits me, I like to watch the road when I'm turning. I guess if you get an aftermarket ECU and then a proper dyno tune you shouldn't need too many gauges. It's not like the A/F ratios are suddenly going to go all over the place and if you run an EBC your boost should be okay. Maybe a small panel with some sort of LED system to warn you of problems such as overboost or leaning out would be handy. You could make it fit in a single DIN unit and if you get a warning you refer to your ECU codes. I don't know, just an idea.
installing them into the DIN isn't hard at all, if you know electrics. But installing the senders may be a little difficult if you're not mechanically capable.