I didn't realise it could be so complicated.
As stated by many above, all modern conventionally configured civil transport aircraft operate with a downforce (negative lift) on the tailplane. The only thing that varies is the amount of downforce and that is influenced by the aircraft's centre of gravity (the further aft the c:g the smaller the required downforce).
For pilots stability shouldn't be an issue unless you're in the business of operating your aircraft way outside the published c:g limits.
MT