Busted out the chalk and dialed in at 35psi in front, 30.5psi in the rear. Previously, I was running 32 front and rear for regular road use. This adjustment gave a pretty good balance between over and understeer.
(For those who don't know, you can mark the tread and sidewall of your tire with a line of chalk and corner quickly to see how much of your tread you are using, and whether you are rolling onto the sidewall at all. Then, adjust the tire pressures appropriately.)
After sorting it out, I took out the spare tire, jack, lug wrench and my ~30 piece socket set from the trunk, which total at least 30lbs. The added lightness in the back with that same pressure setup seemed to give me much more oversteer, especially under braking as the tail end lifts up a little more.
How it felt:
All in all, this was a lot cheaper and easier than buying and installing a brake proportioning valve. 10/10 would recommend.