Thanks again to everyone who replied!
8lbs ended up being spot on.
The dive was fantastic. The lake (up near Bancroft) was quite shallow and super warm so upon arrival the dive plan time was extended to however long the air lasted. We got in a good hour and 15ish with 500 to spare on the AL80 hovering between 12 and 26ffw.
I had a few stare downs with some humongous and curious smallmouth bass (one of which we caught and ate later - scouting mission accomplished haha) and chased some rather timid northern pike around the weeds. Didn't catch any pike after despite some serious effort. They were very cool to watch underwater though - they were patrolling around the outskirts of a huge school of baby perch and bass in the weeds. Totally reminded me of the video I've seen of sharks swimming around the outskirts of the reefs.
Highlight of the dive: Stopped to hover about 6in from the bottom in the weeds to practice buoyancy for a good ten minutes and after about 7min of floating motionless in the water column a monster pike swam up to a dead little perch hidden under some weeds I hadn't even noticed myself. He went completely perpendicular to eye the possible snack close up, mulled it over, and eventually lost interest continuing on his patrol right by us. He was the biggest underwater creature I've seen thus far and some interesting behaviour - definitely a cool reward for buoyancy practice!
The other success was keeping the hands folded together for (almost) the entire dive. I did hand fin a couple times, more out of instinct(?) than need.