I think it comes down to how you treat the tires.
Heat cycle, shaven, tire pressure.
I’ve read that the RT-615s get very greasy at middle of its life. Not sure if that is true or not since I have not driven on them yet but that seems like a big concern to the auto cross people.
Those 3 factors can change the characteristic of the tire DRAMATICALLY. Play around with the RE-01rs and research on tire pressures that have worked for people in the past.
Maybe its when the tire gets shaven, that it shows its true capabilities. Last time I chatted with you, you just ran the tires as is with no heat cycling nor shaving them.
If you find anything interesting in your research, let me know on MSN! I’m quite interested as well.