Hi Kristi,
I'm Yixin, from Doug's lab. I have been working with pDM310 lately to use doxycycline to induce expression of hairpin genes in this vector. I used 10 ug/ml for my studies(though I did try between 0.1, 1, 10, 50, 100 ug/ml. 10 ug/ml works well for my cells). The cells are treated in Doxy for at least ~7 and more days to have about 60~70% RNA knocked down.
Hope this helps.
Yixin