fitted mesh in SL

So after working for some days I came to some conclusions: I have not found a solution to weighting proper both for enlarged breasts and  buoyancy, as they need a different system of weights to go from small to big ones or from "low" and "up" breasts.
Avastar works properly , even if it gives me messages of error.
If you haven't a mirror mesh it is not possible to use X mirror in weights , meaning the dress of the picture below is not properly mirrored because of the scarf on the neck , as I removed the faces below.

Here you can see the model in the beta grid ( different r and l shoe, yes, I did not mind changing them). It works properly.  It is more or less what you see in Avastar , but not exactly.
Below same sl official browser, normal grid

 The shape was slightly different, but the dress behaved anyway in a different way, not following the breast enlargment as it did before. True I also fiddled with mchest and other bones as fitted bones seemed not to be precise for the back of the dress, no way to paint a proper alpha.Same on the hips, they look ok in Avastar, do not in sl as the avi comes out. Or maybe I was so busy I forgot to press alt Q ( remember, the important keyboard shortcut to update when you are weighting). Will keep you posted about that. Blender crashed when I tried to save and close the program.
Then I tried in Phoenix, as I wanted to take a proper picture, but I have not updated to the latest, and I am not sure it can see fitted mesh, so this is the result

Which means that if you buy a fitted mesh dress you run the risk to be seen  this way by those who do not have the latest  or official browser.   The latest Phoenix with fitted mesh is out
http://wiki.phoenixviewer.com/firestorm_release_4.6.1.40478_change_log
but I have not installed it yet.
Imagine going to dance or to a concert where people can still have old browsers.
There is also a strange glitch in the dress I made, which is properly uploaded as a usual mesh, but if I texture it with a png  look what happens if I rezz it :

The mesh is the same, png in blue textured, worn, and looks normal, same texture colored in pink, and no texture on the left. If you use a jpg no problems , it looks ok even rezzed.
Any feedback is welcome
So here is what happens in Avastar

As you can see , the problem is about the same, so I tried all possible bones as below

butt is not enough

so I tried with mpelvis, same result

pelvis

upper leg did something, did not dare to see what happens if you sit down

lower back seems to be what disturbed. It can be noticed there is a line on the waist, like in sl avi, not sure why