Doughnut wings will get your legs up
Unfortunately it's not so simple. You have to remember, that at the start of dive buoyancy of your BCD is much bigger, than in the end of dive when your cylinders are near empty. (I don't mean the
maximum buoyancy, but the actual buoyancy in the certain moment of the dive).
I'll try to explain what is the problem, but at first three fundamental rules of trimming:
The first rule of trimming is: The BCD is not a "trimming device". The only purpose of the BCD is to compensate the gas in your tanks and eventually loose of wetsuit buoyancy if you don't use drysuit.
The second rule of trimming is: The centre of buoyancy of the BCD must be in exactly the same place as centre of gravity of the gas in the cylinders.
The third rule of trimming is: Use weight for trimming.
If you use the BCD for trimming, you'll never get perfect trim for the whole dive. Why? If you do that, in most cases you'll get the relation between centre of buoyancy and centre of the gravity like on the right picture here:
When you start the dive, your cylinders are heavy because they are full of gas and you have also a lot of gas in the BCD. If you'll trim perfectly in such configuration, when you use most of your gas the centre of buoyancy and centre of gravity will move and you will loose your perfect trim. Of course many divers gets perfect trim after playing with moving BCD/weight until they succeed or use the drysuit for help, but the shortest way to get perfect trim for a whole dive is to forget using the BCD for trimming and at first achieve perfect trim with empty cylinders by moving the weight and then fill the cylinders and properly position the BCD to keep the perfect trim with the full tanks.
The second issue is the BCD's shape. The following picture shows the problem of trapezoidal BCDs:
As you can see, the centre of buoyancy is far from centre of the gravity, so it will solve the problem of the heavy head or heavy legs, but only for the first part of dive. Why? Because in the end of dive the BCD is near empty and it stops helping
Some of wings are very square. Unfortunately they aren't so stable as they should be, because when diver gets more vertical position, the centre of the buoyancy tends to move rapidely to the front or back:
Thinking about all of these issues, the most perfect shape for the BCD is symmetrical like on the following picture: