If you do consider using HP5, try comparing two rolls taken of the same subject under similar lighting conditions. Develop one in XTOL stock and the other in XTOL 1+2.
The former dilution will have finer grain but less acutance, and vica versa. When having to trade off grain against acutance, I prefer more accutance. My current combo is HP5 with XTOL 1+2. My Normal ASA is 320 (by comprehensive testing).
Barry Thornton in his book "Edge of Darkness" spends a great many pages explaining and showing why achieving high acutance is more appealing than the sole pursuit of ultra fine/low grain.
My favorite use of Xtol was replenished. Got both the advantages of straight and dilute at once.
Mark Barendt, Ignacio, CO
"We do not see things the way they are. We see things the way we are." Ana´s Nin