If you have time and inclination to type, I'd like to hear more about what he said
Pretty basic common sense stuff:
Pockets - cause drag. Reduce size or eliminate.
Hoses - even an LP hose "out in the breeze" will cause drag.
Only carry what you 100% really need. For example, you won't always need a compass or back-up mask.
Wetsuits - less drag than drysuits. This, I've experienced. I decided to use AL80's in North Florida caves when teaching or diving at the Intro to Cave level. Strangely, when guiding Intro divers in wetsuits & in twin AL80's on 3rds dives, we were getting farther than when wearing HP100's in drysuits.
Dive the cave. Equip for the season, duration, and mission.
Delta-shaped wings seemed to be performing better, but the jury was still out.
Other stuff would spark a lot of heated debate. I'll leave it out.
Seeing Bill's rig, was just impressive because you could clearly see what he reduced to the smallest items, how he repositioned items, and what needed to stay large, could be reduced, or eliminated. He told me it's always a work in progress.