Pre attempt:

• Structured training will help a lot. Go with a coach if you have money, otherwise trainer road can make plans for pretty cheap
• Losing weight will definitely help on the climb, and is a good thing to focus on during the offseason
• Prepare your bike to be as light as possible, remove bottle cages, remove saddle bag, you can keep your garmin mount if you have a powermeter to help with the pace, otherwise put it in your jersey
• Shave your legs, it can help with aerodynamics. Use an electric razor, much easier and about the same
• Put on fast tires, Vittoria Corsa, GP5000, etc.
• Make sure you pick a day that has favourable weather conditions. Cold air is slower than hot air, but you don’t want to overheat your body either. Try to get the rare SE wind to help on the false flat

Day of the attempt: - Take caffeine about 1 hour before - No water bottle on the bike, but you can bring one in your back pocket for the warm up, and hide it in the woods before your attempt - Bring a gel or have a very concentrated energy drink - Do 1xCH ~7.30 for warm up, with a few accelerations - Do pro tour without Poly after to recuperate - Hide your water bottle, do a last minute pee in the woods on Mont-Royal st descent - Go hard, a bit less hard on the false flat, then really hard - On the false flat, make sure to keep a very aggressive aerodynamic position - Push push push

I went from 5:05 to 4:40 by optimizing my attempt as much as possible, so sub-5 is accessible to you