Mikedavid, the humidity cannot be what you suggest. In Canada, during the winter months the humidity is very low due to the air's inability to hold moisture at low temps. The only time you would find 80-100 percent humidity is in the summer, and only outside during a rain storm. If you can get your humidity up to 35 percent in the winter and maintain that, and keep it at 45 - 50 percent during the summer, you will have no problems.
BTW, I am in Toronto (sorta) and am responsible for the installation of about 12-15 floors per day, on average.

Ok Then I have a huge question.

All the local installers I speak to tell me that it's OK to staple the flooring directly into 5/8" waferboard flooring. They insist on it almost.

What is your comment on this?

The "staple versus cleat" debate is ongoing, with no clear winner.
My personal thought is that if i need to hold a few pieces of paper together, then I will use staples. All of the floors installed by the company I work for are held down with cleats. This is a policy that I established, and it is partly due to the fact that cleats allow for more non-destructive movement in our extremely variable climate.

Second part of your question, 5/8th inch waferboard is not a sub-floor, it may be used behind a brick wall but I certainly wouldn't install a floor on it. 5/8th inch OSB on the other hand, has been accepted by the building code writers here in Ontario, most likely due to pay-offs by the manufacturer. While we won't install directly over it for a private customer, we are obligated to do so for our builders due to contractual agreements.

Two of our larger builders use it (no names to be mentioned here), one builder substitutes plywood when the purchaser chooses hardwood, and the rest; oddly enough, took our recommendations to heart and only use 5/8th inch plywood ove joists spanning 16 inch centres.

You're right about the cleat/staple debate Dennis. My preference is using staples spaced 5-6" OC over any OSB product.