I never expected my "Hawaiian shirt" concept to garner the attention that it has. Let's hear it for a good catch phrase. Since there's obviously interest (mostly vitriol), I'll add some detail.

For about twenty years now, I've been riding with a backpack on. I have a health condition that makes it very problematic for me to be away from food and/or medication for too long. So I travel with lots of repair gear, a bag of almonds, some lifesavers, and medicine. I've come to view the extra weight as just extra training resistance.

The backpacks that I wear have always been some version of the Deuter Air backpacks which have a mesh screen that separates your skin from the backpack proper and promotes some degree of ventilation. I love 'em. Wearing these backpacks:

1) Reduces the flapping of my loose clothing and;
2) Reduces the effectiveness of my ventilation program although not enough to truly compromise it it seems.

So that's how I deal with the flapping, to the extent that I do.

My approach to heat management originated back in 2014 when I did a summer tour of Southeast Asia as a ride along on one of my wife's business trips. I've always struggled in the heat and never so much as I did on that trip which included:

1) A bike tour of the Mekong delta where I thought that the Canadian embassy might have to helicopter me back to air conditioning.
2) A Ha Long Bay boat tour where I had to alternate 20 min periods on deck with 60 periods hiding in our air conditioned cabin in order to survive.

I brought a bunch of expensive athletic clothing on the trip made by Nike et all, expecting that they surely offered the best cooling solutions that science has to offer. This didn't work at all. Instead, it felt as though I was 24/7 trapped within a sponge that had been soaked in 40C water. Out of desperation, I looked around to see how, for goodness sake, the locals were surviving the summer heat:

1) Wear a loose fitting shirt that mimics a Hawaiian shirt,

2) Wear shirts of silk or linen, not cotton. The Hawaiian shirts that I've mentioned are made of these materials.

3) Learn to operate a hand fan in such a way that you can do it for hours without tiring your wrist or expending a lot of energy. On a bike, this is just the wind, natural and Harold made.

4) If it gets really bad, soak a small cloth and place it on the back of the neck for evaporative cooling. On a bike, I mimic this by wetting the collar of my "Hawaiian" shirts.

As you can see, I adapted every one of these strategies to my bike riding. I may be a "Zoolander" when it comes to my level of sophistication as a cyclist but I'm not such a fool that I don't adopt strategies that work when I witness them working for myself. And I fully acknowledge that there may well be cooling strategies that work better than mine that I've simply not tried. At the same time, what I'm currently doing works well for me so I've not been actively seeking out better strategies. Life is filled with challenges; when I feel as though I've got one licked, I often just move on to the next.