I have previosly posted the
MOST complete list of all WM5 hacks/tweaks available including those of which will speed it up by ajusting several caches.
However, to fully go a step further you need to overclock your PPC by using a 3rd party app. I use
Pocket Hack Master and I went from 416 to 520 to 624 and there is a big difference. PM me for more help/details.