First, I'll address the bolus and intervening drink changes. In the R. v. St-Onge decision, the Supreme Court repeated its criticism of both of those defences.
You will perhaps want to hear from the alcohol test committee, but it is my understanding that a person downing several drinks and getting into his or her car represents a danger to the public, even if he or she hasn't quite gone over 0.07%.
The proposal to have the offence being 80 milligrams or over within two hours actually follows a common model in the United States and other countries to get around that issue of, “Was I just under 80 as the police pulled me over?” That's more a matter of a public policy issue.
The 84% is well above others, but we are dealing with a situation in which, in the overwhelming majority of cases, the person has been found behind the wheel; the police officers have developed suspicion; the person has failed an approved screening device, and he has been shown to be over 80 milligrams on the approved instrument back at the station.
Consequently, 84% is nowhere near the United Kingdom's 98%, and its laws are similar to ours.