The majority of the posts have been "Always use a condom unless you and your boyfriend are tested" From what i read they are tested, Top is Neg, bottom is Poz.
Now let talk about risk, everything you do in life has a risk, something more than others. Living in LA has a risk, so does living in the country. Just different risks. Not too many street gangs in rural Wyoming, there again few people have been killed by a tractor in downtown LA.
If you are Neg and a Top you partner is Poz, bottom and undetectable they chances of the Top contrating HIV is so so small it is almost not work talking about. If the bottom was Neg and the Top Poz and undetectable current stats suggest that the chances of the bottom contracting HIV are small. That being said the statistics are only suggesting this, no formal study has been done for obvious reasons. HIV follows the line of the body fluids, so if the Top is fucking the bottom 99% of the fluids are going Top to bottom. There are issues like Tops with foreskins (wash under your hood good after just to make sure none of the bottoms fluids remain)
In the end, we all have to decide what risks are acceptable and which ones are not.
Oh and for the record. The pups Master fucks it bareback all the time using only spit for lube, pup alergic to most lubes, has been for 5 years now and he is still Neg. Your milage may vary….