Some points to consider:
-Lift is more critical at the beginning of the dive because of the weight of the gas in your tank. An AL80 will swing from approximately 3 pounds negative to approximately 3 pounds positive.
-Ballast is more critical at the end of the dive because your tanks tend to shift towards the positive as you breathe them down.
-3 pounds of lead per mil of wet suit is a rough starting point for figuring out ballast. A 3 mil wet suit will need approximately 9 pounds of lead, a 5 mil will require approximately 15 pounds, 21 pounds for 7 mil. These are rough starting points that will require you to adjust as necessary.
-A 7 mil wetsuit will compressed to approximately 3 mil in thickness at 100 feet.
-A brand new wet suit will be more buoyant for the 12-18 dives. After it gets crushed by the depth after a few times it will stabilize in terms of buoyancy and you should be able to dial in your final adjustments.
-A stainless BP/W set up will weigh in at approximately 8-10 pounds.
-BC's are made to be a one side fits all solution. BP/W's are meant to be a modular solution allowing you to go from single tanks to doubles and scale your wing up or down to suit your dive.
-An oversized wing will produce excess and unnecessary drag, trap air making you unstable, and generally be more difficult to attain proper trim and buoyancy.
I can Side mount 2 AL80's in saltwater wearing a 3 mil wet suit with 2 pounds of trim weights on the shoulders and a small wing that provides about 15 pounds of lift. That set up results in about a
10-12 pound swing in terms of gas. That whole rig, minus the trim weights weight in at about 4-5 pounds. I don't need a lot of air in the wing to maintain buoyancy and when those tanks are empty I can hold and maintain buoyancy in about 5 feet of water with zero air in the wing.
My wife dives a BP/W in a 5 mil wet suit in fresh water. Using an AL-80 she needs about 2-4 pounds of lead and that's mainly for when her tanks are empty. Wearing a 3 mil in saltwater she only needs the weight of the BP/W.
We're doing a live aboard in the Galapagos in Oct, of 2019. At present the live aboard will not let me side mount off it so I have to go back mount(yuck), which will be a BP/W. I'm planning on using a 25 pound wing with a dry suit for that trip.
Personally, I think you'll be fine in a 25-30 pound wing. It should provide you with plenty of lift yet is not so excessive that it gives you stability and trim issues. Additionally, I think you'll be a little more streamlined in the water and might see better air consumption as a result.
Hope it helps