[oldschool]

In dash instruments like speedometer, tachometer, fuel, engine water pressure, engine hours, trim gage, amp meter, etc are good. Sonar/GPS units are better mounted so they can be removed easily for trailering, storage and maintenance. The heat under a cover and road vibration is the main cause of failure of sonar units. I would suggest you think of something else to cover the hole, like black Plexiglas with gageslike live well water temperature gage or something else you may need.
Buying a good sonar/GPS is one of the most important tools a bass fisherman needs and should be controlled by the dash hole size.
Tom

 

[oldschool]

To the best of my knowledge the "reset buttom" for marine electronics is the 3 amp in line fuse. Lowrance will up date your sonar units by shipping the unit to them and I have been doing this for over 30 years. Contact Lowrance and ask for Darrell Rollins. 918/437.6881
Tom

 

[oldschool]

Added thought; I use RAM adjustable mounts and add a rubber bumper under the sonar unit to protect boat if the mount loosens in rough water. The RAM mounts allow you to position the sonar unit where you need it, away from trolling motor cables and to one side of the consul so you don't look over it to see where you are going.
Tom