He better get it right !!
The HP cam on the Outback is pretty much.......draw specific ! So if you order a 29" ..........it's a 29" ! Most of the OB come with an 80% let off cam .............it has a draw stop adjustment that lets it go to 65% and your draw length shorten's by a half inch ! Your pretty much shooting off the wall at 65%........I can't imagine many people liking it !
Also the bow has a 10lb range..........so if you order a 70# you can go to 60 # , order a 60# you can go to 50#, etc. ! Most of them run a little heavy .........so if you wanted to shoot like 63#.......it'd probably be better to get a 60# one and max it versus getting a 70# and cranking it down !
I'd tell your dad to go get measured at a pro shop before ordering and be pretty sure of what poundage he wants to shoot !
Good Luck !