Testicles chafing on legs - are my bibs too loose or too tight? Some context - I have a pair of bib shorts that fit me well though could certainly be tighter without causing discomfort. I have a good bike fit, and I can do 100km+ rides without saddle discomfort.

A few months after I got the bibs, this chafing began little by little. My testicles rub against my legs as I pedal, and I end up with a sore/raw spot on the outside of each one. I begin to notice this after about 40km on most rides.

I have tried different 'positioning', but they end up back in the same place (does this mean my shorts could be too loose?).

I never had this issue riding with normal shorts, nor with my old pair of padded shorts that were too loose for me.

I've found I can alleviate this somewhat by pulling my bibs down a bit, simulating looser bib straps. It seems that the tighter the bibs are, the less space there is for my junk, and the more my testicles are pushed out into my legs.

So, are my testicles supposed to touch my legs, at least during part of the crank rotation? And should I get an even tighter pair of bibs?

I've been resisting resorting to chamois cream, I'd like to solve the root issue if possible.
"we're all adults here..."

In my experience, when riding with bib shorts or cycling shorts, they have to be pulled up, way up.  And they should be a snug fit around your lower body - the shoulder straps are more forgiving.

Ideally your pants cloth should be in contact with your skin all the way up your thighs and right up to where the skin turns around and comes back down as the scrotum.  (sorry I can't find a medical name for this crease in the skin.)

This should leave two layers of cloth between the boys and the thighs.  

Chamois cream might help, but you won't know till you try it.  Vaseline / Petroleum Jelly is worth trying if you already have some (most households do) but its not as good as the proper product.