I have in my files a document that gives a formula for calculating blood alcohol levels.
(It is not to be taken as anything other than a contribution to the debate, and above all nobody must think that it gives them a way to compute what is a safe level of drinking).
Here goes:
Blood Alcohol Concentration (BAC) equals weight of consumed alcohol in grams divided by body weight of subject in kilos multiplied by r.
r is 0.68 for a male and 0.58 for a female, being an estimate of the proportion of blood to bodyweight.
NB: the specific gravity of ethanol is, I am told, more or less .8
Now I am no scientist, but those out there who are might be able to work on the above to give us an idea of how much 13% ABV wine a 75kg man can drink to get to 20/100 in blood.