Oh, there is another good reason to avoid loose shorts for anything other than short rides: chafing. On a bent you don't have a saddle keeping your scrotum away from the sides of your legs.
At the least, if you wear loose shorts, at least wear some tight, supporting underwear under them. I use snug synthetic (wicking) briefs. Champion brand, and others.
It also helps to make sure when putting them on to pull them up tight around your junk - up, and centered.
The sides of my scrotum practically wore through on one long sweaty ride one day (12 hr race; Calvin's Challenge) because while I did wear the above described underwear, either I didn't take care to pull them up appropriately, or perhaps they sort of slid downwards over the course of the ride. The sides of my scrotum started rubbing on my legs with every pedal stroke and I didn't notice it at first. But the post-ride shower was quite painful.