Thanks for the feedback, Jess! According to the analysis I just had done (just had the phone interview yesterday!), my roots ARE low-po, and my length/tips are high-po. So... there we go.
And yes, I am a cowasher. I co-wash pretty much daily, and will spend much of my 3-minute shower massaging with my finger pads. It works great, but the hair doesn't really absorb much (water, condish, product... whatever!). But the virgin hair doesn't really have an issue, either. It feels great and moisturized always, regardless of if I've co-washed or not, or if I've saturated the hair or not! It's a good problem to have... I expect that my hair will be rather low-maintenance when it's all virgin.
What I'd love is for the lighter products which work great on my roots to work well throughout! But after experimenting for a few days, I think I finally found it! I tried a homemade FSG -- which hasn't worked well for me in the past, but I made it really thin and added gelatine. It's AMAZING so far!
Thanks for the help, all!