Line size makes a big difference as well. Your initial thoughts do not seem correct though. With 10 pound Mono @ 1.5 MPH with a 6 ft leader from the 2oz weight it would be 83’ to get down 35’.

I recommend a trolling app called Troll Master. It lets you input all the different variables such as leader lengths and trolling weights and calculates the line out required. If you do any fishing in the central basin the precision app lacks the ability to use different lead lengths and also for 4 and 5 ounce snap weights.