minimum protein conc for immunoprecipitation - what's the minimum needed for results (Jul/25/2008 )

Hello,
I need to run an immuno precipitation with nuclear protein extract. however, I got pretty low yields, and am contemplating whether to continue on with the immunprecipitation or to seed another plate of cells and treat accordingly so that I can get more nuc. extract.
This would put me back another 2 days, however.
We normally use a minimum of 20 mg, but in my lowest concentration the most I can get from it is 7 mg. Would this be a pointless amount to experiment with?

Thank you.

It really depends what you're detecting at the end of your IP.
We NEVER get 7 mg of protein at any stage. Usually we use 150 ug for IP to detect with western afterwards.