Re: F150 low clearance
Depends on your use I suppose, 8" is certainly a reasonable amount. If you want to go rock-hopping or severe off-road use (which would possibly include some aspects of farm use for example) then more is always better!
If you've come out of a car then I would guess it won't be a problem. It is worth being aware of the underbody layout and where the low points are, so if you are in marginal terrain it will assist in picking a line through it.