Let me see if I can help with the confusion you might have got from mine and others answers.
Let's start with the manifold - My reply was that I used Dive Rite manifold without any issue with those kind of tanks while other poster described how challenging might be the use of OMS manifold with these tanks having non standard diameter.
Given two manifolds not only come from two different manufacturers but also have two different constructions, this should provide you with excellent data point which manifold type might work for you. DGX currently sells a manifold for $99 which looks and, according to other posts on this board, is a rebranded Dive Rite which means this should work for you as well.
The combination of tank weight, its buoyancy characteristics and the impact on diver's trim are very personal since we have different body characteristics and use different equipment setups so you can't expect an absolute answer here
Let me describe to you my personal experience with those tanks and why they don't work for me as doubles - Let's start with those tanks weight in water. They are at least 4 # negative when empty (btw I believe that this is without valve, I think with valve it is another pound). Other tanks in this category are about 1 pound negative (including valve) which means for doubles you have additional 6-8 pounds of non ditchable weight using those tanks
With those tanks doubled I found myself having a balanced rig with just a soft plate and no additional weights needed BUT I personally was head heavy (after shifting tanks in bands and moving my wing, etc). The only way for me to fix my trim was by attaching additional weight to the lower part of my rig which means now I don't have balanced rig anymore and I end up overweighted.
Since most of us are using hard plate (aluminum or steel) that are more negative than a soft plate, it makes the problem even worst. This also affects the size of the wing I need to use to compensate this weight. Hence for doubles, I ended up with tanks that are less negative and that allow me to shift some weight around for a proper trim without getting too overweighted
This might not be the case for someone else but this data can be important if the only way to fix trim requires attaching additional weight like in my case.
There is no one correct answer to almost any question, we share a lot of good information based on our personal experience. As divers, we have the responsibility for all diving related decisions including our gear choice; I find that data shared on the board does help me with making better decisions
Dive safe
