I hear a great many grumbles about blurry gauges and such when using a HMD. There is then a whole bunch about maxing antialiasing and all the other names it goes by. In my experience, turning off all antialiasing options provides a sharper image for me in the HMD. All the antialiasing options and levels I've tried and compared seem to have an overall blurring effect to get things to look smoother. On high rez monitors, I think they can make up for this with the extra pixels, but for the limited rez of our HMD, we can't make up for it. Without any AA, I can see the steam gauges on my C172 clearly. Try it out and see. I'd be curious if anyone else finds an improvement.
One more thing. I don't know if it's just the people I've watched use FlyInside on youtube or not but I don't see anyone adjusting their seat. The game has the seats sitting as far back as possible. It's one of the first things you adjust in a real plane when you get in. If you aren't doing so, scoot your physical chair forward in the real world until you think your feet would actually touch the in-game rudder pedals. This will set you closer to the things you need to see better.