(In our opinion they run on the small side.)
5'8" Tall JP on the Yamaha SDuro 48cm size Haibike AllMtn 6.0, a great fit.
5'11" Tall Shea on the Yamaha SDuro 48cm size Haibike AllMtn 6.0 which is the size he prefers as he likes to catch big air and whip the bike around so he likes a little smaller fit. If Shea were going for just fast XC riding should probably be on the 52cm.
6'4" Tall Nick on the Yamaha SDuro 52cm size Haibike AllMtn 6.0... a good all around fit although the pic does not convey that as he does not have his foot all the way extended.