I didn't notice the lack of VSI on the ICON panel.
Let's see if I have got this right - light aircraft are flown mostly VFR, that is, looking outside like when driving a car. One may look at the speedometer to see how fast one is going, or the fuel gauge, but the rest is visual. A striking example of this was a recent Red Bull Air Race crash in which the pilot says 'I broke my own rule and looked into the turn' I take it he lost his visual reference: in any case he banked past vertical and levelled the wings just in time to crash into the water. Fast ailerons on that thing. He was using any of the instruments, I think.
https://en.wikipedia.org/wiki/Adilson_Kindlemann
IFR is like driving your car in a fog? Quite unnerving. I remember being in a commercial airliner in a night flight and there was no way of telling where we were or what way the wings or nose was pointing, granted there were not many possiblities, but it was very unsettling.
Since in IFR all you have are your instruments. This is where I would guess they should be nice and large and easy to read.
Take a look at this syntheric vision panel. Nice and large, however the numerals seem too small, and not striking enough. My other contention is that a curved dial is easier to 'place' than a straight up and down ribbon readout as seen here. For example for the ASI readout on the left side of the display.
http://www.aviationnews.eu/blog/wp-c...ew-cockpit.jpg