Some thoughts on being short stacked?

[Danger]

I posted some of these ideas on another forum but did not get the replies I wanted(members here are better at using math), but...

I was playing in a online no-limit hold'em tournament and I like to keep track of how I'am doing verses other stacks and the blinds(more so when I short stacked). I heard once that when you are at about eight times the big blind you are pretty short and should be looking for a good spot to get your money in. Well in this tournament I had a tough beat(a 5 outer hit), and I was at about eight times the big blind when the antes kicked in. I had no way to account for the ante, but I knew they had a large effect. So after the tournament, I got to work trying to find a way to figure in the antes and I came up with this:
8*BB + 5.33*N*A = Short Stack
BB = Big Blind
N = # of players
A = Ante
The formula assumes the small blind is half the big blind.

Tell me what you guys think of the formula and if you want me to show you how I came about it, tell me and I will post it later.