Mine are 2", then 10" down. If I'm just using 1 grate I always use the lower one.
You'll be fine, just keep poultry below other foodstuffs if cooking at the same time
(which can be a b!tch if the chicken is done first, and you have to lift everything else out first to get at it).
Enjoy your UDS!
1 x UDS, 1 x 22.5" Weber kettle, 1 x COS(for storage), 1 x Kingsford SJS knockoff, 1 x ailing 2 burner gasser.