Sig,
Kate and Mike has good points, I origianlly had issues with the push forward as well, but found that in between you learning how to work the bc and getting your weighting dialed, it will go away - I have spent the last 10 dives just tuning weights after getting a new dru suit, so it may take some time to get everything just right.
As far as the Ranger goes, I have looked at that BC - I personally currently dive a Dive Rite Transpac II, which is fully modular and allows you to replace the wings and add things to the belt - a ranger does not have this flexibility.
However, what really had me drop the ranger from my consideration, is the way the ditchable weight system is setup, there is a pull cord which runs around your back in order to ditch the weights on your right side, this pull cord look very much like what you woudl see on a parachute. My concern is that this may work really well in "air", but when you have water, and a tank pressing agains your back, this pull cord may not pull very well if you understand what I'm saying - something to think about.
As far as the Duo air, I would be cusrious if that happens to be the BC the guy has in stock - if you want another one he may have to order it and that means that he is not reducing inventory to get it... Conclusion, he may not neccesarily be selling you what you need, but what he want you to buy...
I think you should do yourself a favor and look into the back plate concept as well as the Dive Rite Transpac II as they are much more modular than the Rangers...
If I ould go out and get a rig romorrow - I would get a back plate over the Transpac II though.
hope this helps,
Terkel
ps - congratulate Kate on her new Dry suit...