As a general rule, I keep up with the flow of traffic. On my first IBA ride, I took a route through Florida on the Florida Turnpike. It's a toll road, but beats the hell out of trying to get to the keys without it. Speed limit there is 70 mph. Most people are doing 80-85, some up around 90 mph. Riding at the speed limit there would result in a very unpleasant meeting with other motorists. 70 is simply not safe. On that road, I kept up with the typical flow of traffic (around 80 to 82ish mph).
I don't think the IBA would have a problem with 10 km over. 15 is probably okay too. 30 km over is a bit excessive IMO. If your speed is likely to get you a performance award, it's too fast as far as I'm concerned. I would expect a conversation with a mountie at 30 kph over.
I can promise you, making the timer is the easy part. Anybody can do 1,600 km in 24 hours. That's an average of 66 km/h. Including typical food and fuel stops, that's easy to maintain. 100 km and up is typical for Canadian roads, right? The hard part is staying on the bike. Your butt gets sore. Your legs are stuck in the same position all freaking day long. It's very tempting to take more and more breaks just to get off the bike. Heck, my fuel stops got more and more frequent and longer in duration as my rides progress. The key is to just get back on the bike and finish the ride. (As long as you're not too tired or fatigued. Stay safe)
Going faster doesn't really save you much time in the long run. It burns more fuel, which makes you stop more often. It's also harder on your body, which means you'll be more fatigued than taking your time and slowing down. Riding 100 mph doesn't make sense when it costs you three additional fuel stops. Everything you save by speeding, you lose in additional stops.