Here's the info I mentioned earlier supplied to me by a professional Landscaper.

"It is more the case that over application has no extended benefits because the intention is not to poison the plant or the soil but alter its structure.
A systemic herbicide kills the weed by altering it's hormones and blocking the enzyme that the plant needs to photosynthesise.  Once photosynthesis is restricted the plant cannot produce starch on which it can feed and it naturally dies.

Over application will just waste material but some plants, perhaps woody stems are less sensitive than grass and will need a higher concentration. The same applies though. Once the recommended rate is applied, adding extra to this rate will not effect a greater control"

The ideal would seem to be the one you recommend i.e. 200ml in 16 litres (or 125ml in 10 litres) which is 80:1  This sits nicely between my economic 100:1 and the stronger mix of 50:1 which I use for more pernicious weeds or with a brand that seems to be less effective.