Improving transient CHO protein expression - (Aug/19/2009 )

I have started using Invitrogen's freestyle CHO cells (without serum, and in suspension) but the protein expression levels are not great compared to the HEKs I was using before.
I have played around with ratios and have an optimal ratio (1:1 with 1ug DNA and 1ug MAX transfection reagent). I have also tried putting the cells in hypothermic conditions which appears to have increased the expression by almost double, but this still isn't quite enough.

Any other suggestions of something I can do (without extra cloning) to imrpove the expression of the cells?

Its hard to beat the transfection rate of 293.

Have you done any EGFP or beta-Gal transfection to test what % of transfection do you have?

It is hard to beat it I know, we had the wrong glycosylation patterns though. Just want to up the production as much as possible.

We transfected with GFP, gave about a 60% transfection rate.

Anyone who has any expreience with mammalian cells can help though, I'm not just looking for tricks specific to CHOs. I will try anything that has been shown to work on mammalian cells.