You will find that weighting for a drysuit varies wildly depending on the construction of the drysuit and the type of undergarment you use. If you dive a neoprene suit, it will take more lead to sink than a trilam. The thicker the undergarments, the more lead it will take. Different materials used in undergarments will require different amounts of weight. You should be able to figure our the weight shift in your tank from full to empty. You can also put your DS and undergarments in a trash bag, squeeze all the air out and then see how much weight you have to stack on it to sink it in a pool. Or you can just guess on the ds/undergarments for a starting point.
I used a "best guess" for my starting point and then hit the quary with a weightbelt. After a few dives I figured out how much lead I needed. After that, I started experimenting w/ weight distribution for ideal trim. After some trial and error, I ended up w/ a 7lb assymetrical v-weight and a 4lb tail weight, plus I moved my wing up one notch. This keeps me horizontal in my 108's without being head heavy/feet light. I ditch the tail weight w/ my 85's and get the same effect.
All in all, it took me about 5-6 dives to get it squared away. I prefer not to wear ditchable weight in doubles so I took a little more time to work out the ideal weight and trim. If you are just wearing it on a weight belt you can get it nailed after 30 mins in the pool.