I am sure 24" will fit, but it seems a little large considering the folks in the bunk are less than 6' from the TV.
If my son is in the bunk his feet would probably get in the way of being able to see the bottom of the screen.
2014 Georgetown XL 352QS
2013 Days Camped-10 (in a rental)
2014 Days Camped-52
2015 Days Camped-53
2016 Days Camped-32