V4, M4, etc import into Blender with the origin/center at the 0,0,0 point so there is no need to muck around with changing from the defaults for the basic scaling discussed here.

I use the base file set-up method  I mentioned creating for every clothing item and prop I make and it works properly every time for every figure. 

If you import an existing clothing item that has a different origin point than 0,0,0 then scaling around the cursor works well but the discussion at hand concerns making new items.

The problem with scaling around the cursor is that if you get off just a hair when placing the cursor then your finished clothing item will be just a bit off when you import into Poser for rigging. Don't get me wrong I use scaling around the cursor frequently just not for the basic set-up.

Scaling works to the origin point of the active object in multiple selected objects so by selecting the clothes with V4 as the last selected object this makes V4 the active object in the group with the origin at 0,0,0 ensuring that the parts scale to the proper location and import correctly into Poser.  Every clothing part maintains it's own origin and location but this doubly ensures that those locations are in the correct relationship to the base figure prior to export.

The mannequin file you mention saving is the same as the V410xBase.blend I mention so we're on the same page there but we both know if it's not specifically noted some people would go through the whole process every time.  (I did that myself a couple of times when using Compose to make vertex joined and merged meshes to sculpt on before the light came on and I saved the base meshes to re-use.)

My reason for naming the base blend as I suggested is so I know by the file name what the scale factor is because I have base files for various things that are at different scales, keeps me straight. (I've found that Fluid dynamics involving Poser/DS characters work better at a 5x scale rather than a 10x scale for example)

The end result is that you and I both have created a base file to use for item creation that works.

The difference is my method is less prone to introducing user error during the set-up of that base blend because the Blender default settings are used.