I have a Sage 50# and pull right around 28" or a tad less. My favorite arrow for this setup is GT traditional 340, full 32" long, 100 gr brass insert & 200 gr head. Gap at 20 yards is only about 10". So putting the tip of the arrow just under the belly of a deer puts me right in the money out to about 25 yards. Arrow weighs about 650 grains so it has plenty of punch.
I've shot 175 grain heads without any noticeable difference on field tips or broadheads.
If he'd rather go a little lighter & shorter, I've also run GT Trad 400, 29" long with 100 grain brass inserts & 200 grain heads. Much flatter trajectory at about 550 grains or so. But the gap is much bigger -- closer to 20-24" for me.
Just for kicks the other day, I ran some full length GT Trad 400s through on my 45# limbs (50 grain insert & 125 gr heads) and that worked pretty well, too. I bought these for a different bow but that one broke. So this was just for fun. The trajectory was very flat at only about 450 grains total weight but the gap was more in the 12" range -- very manageable combo.
The Sage is very forgiving for me. I can shoot just about any spine arrow with 30#, 45# or 50# limbs and it still hits where I'm aiming (assuming it's fletched). Broadheads make spine much more critical but just with field points & fletched shafts, it's hard to mess up.