Many of the modern avionics and EFISes have their own cooling fans in or on them, and in addition to that perhaps the most important thing is to have some sort of vent holes in the glareshield (or even a couple muffin fans). That should allow that dead space between the main panel and sub panel to be ventilated and kept at a good temperature, so everything should be good (as Bob noted, those glareshield fans also work as defrosters too).
Just my 2 cents as usual!
Cheers,
Stein
Many of the modern avionics and EFISes have their own cooling fans in or on them, and in addition to that perhaps the most important thing is to have some sort of vent holes in the glareshield (or even a couple muffin fans). That should allow that dead space between the main panel and sub panel to be ventilated and kept at a good temperature, so everything should be good (as Bob noted, those glareshield fans also work as defrosters too).
Just my 2 cents as usual!
Cheers,
Stein