H2Andy:next dive you do, get your tank to just over 500 psi and keep only enough weight to stay slighlty negative or neutral at about 10 feet
this will allow you to ascend the last 10 feet under control, or stay at 10 feet indefenitely (well, not really ... but for quite a while)
depending on the dive, you can either put the weight you remove on the bottom while you test it out, or hand the weight to a buddy.
your goal should be to be just about neutral at 10 feet with 500 psi or so in your tank
you can use the 10% body weight formula and then divide than by 2 to get a ballpark figure
for example, at 180 lbs, my 10% weight is 18 lbs. i divided that by 2 (9 lbs) and started experimenting.
H2Andy, your equasion must be for warm water. What I have done for cold water here on the West coast is 10% plus 2 lbs. Example: I'm at 180 lbs X 10% = 18 lbs, then add two pounds to get 20 lbs of weight. This is a good ballpark figure for someone starting out and diving water colder than 70 degrees F.