Welcome to the forum
Answer is it depends on a few things:
Where is it going to be mounted?
Will it need to rotate out for viewing?
How much space is there, where it will be mounted?
Once you have determined how much space you have to work with, your decision on what size should be a lot easier. Even the big fivers we sell seems like a 24" is the most popular size. I have a 24" in my bedroom but I could easily put a bigger one in based on where its mounted.
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2012 Copper Canyon 273FWRET being towed by a 1994 Ford F350 CC,LB,Dually diesel.
Airlift 5000 bags, Prodigy brake control, 5 gauges on the pillar.Used to tow a '97 Jayco 323RKS.
Now an RVIA registered tech. Retired from Law enforcement in 2008 after 25+ yrs.