In my opinon, your absolutely right in your thinking, but it all depends on who you ask! Some halter breeders want N/H horses because they believe the horses tend to build muscle quicker and with less work yet tend to be less symptomatic then an H/H horse. If you want a foal that is HYPP Negative(N/N) then you have to breed N/N to N/N. Otherwise if the mare you are having tested comes back N/H she will pass the gene on to 50% of her foals. It's a dominate trait and only needs one parent to pass it on! I personally would not breed a positive(H/H or N/H) horse even if it was to a negative(N/N) one. I don't know if that was any help or not, its just my opinon!!