Well, I got a reply from the developer (pretty quickly, too...he's in Russia!). If you purchase Pocket Hack Master for the Axim, use MANUAL settings in the XScale settings, as follows:
L - 27
M - 1x
N - 5.00x
Works like a CHARM now...up to 497.50mhz, with auto-scale back when not running processor intensive programs!
Thanks for the suggestion, though, Steve! And thanks for your reply, too, Snack! It's a Dell Axim X5 400mhz, running Pocket Hack Master v2.32