This is a breeders board so I am only talking to breeders or prospective breeders. Learn your genetics.
1. Oversize chihuahuas vs smaller chihuahuas results in C-sections. Size can range for 7 generations. I know they can run $1500.00. in some places. For a litter of 1-2 make sure it is justifiable.
2. Some flaws ALWAYS show up in puppies. Bad fronts,roach back, low tail set. Underbite, it takes 19 copies of that gene to line up to show underbite. 18 copies and it wont show. Lots of times it skips a generation.
But it will come back to bite you in the ****.