I would like to make a gauge cluster for my car out of 1/4" thick wood, plastic, or plexiglass, it will be wrapped in carbon fiber vinyl when finished. Should I use a 3 3/8" hole-saw for a 3 3/8" gauge or should I use a smaller hole-saw and file it? The tachometer is 3 3/8" and my other gauges are 2 1/16".

I'm not using metal or aluminum simply because I don't have any tools to cut nice circles in them.
There are companies that make nice housings but they are way out of my price range(photo attached).