This is why I ask:
Ideally, you'd have players do snow angels and picture the plane of coverage. But it's a puzzle to get to that from wingspan, height, and standing reach. For example, having a long neck helps the height measurement. That helps you see over defenses, and tells us where your shoulder bulks sits (interesting for rebounding). And players with very broad shoulders may have long wingspans that don't reach as high as players with narrow shoulders. The differences are subtle, but I'm still interested.
Take this case:
Player - Barefoot - Wingspan - Reach
Carlos Boozer - 6' 7.75" - 7' 2.25" - 9' 0.5"
Brent Wright - 6' 7.75" - 7' 1.5" - 8' 9.5"
Boozer has a .75" better wingspan. So each arm is .37" longer. But he has a full 3" advantage in the reach. That's a big difference for otherwise similarly measured players. Is that all from narrow shoulders?
Wright had no in shoes measurements for height. Boozer had some bigs ones (added 1.75").
Jeff Green - 6' 7.75" - 7' 1.25 - 8' 7"
Green is down 1" on Boozer's reach. .5" for each arm. But he's 5.5" down on his reach.
All this makes me wonder if Boozer got to wear shoes in the reach while others may not have

"Please note that there were variances with the standing reach measurements for several players in comparison to prior recorded measurements. As a result, the unofficial anthropometric measurements and strength and agility testing results (currently available on nba.com) are under review. The official measurements and testing results will be released as soon as the internal review is complete.”
http://www.draftexpress.com/article/NBA-Draft-Combine-Measurements-Under-Review-5499
So, does anyone know how they handle shoes in the standing reach?