Anyway, I'm having to make due with this old G4 Mirrored Front for now: 2GB memory, OSX 10.5.7 and the older than dirt 1.25 GHz. I have noticed the even further slow down when I went from 10.4 to 10.5.
You didn't mention whether your MDD 1.25Ghz was the dual processor one or the single, but I'll assume it's single.
Thanks for the confirmation of Leopard 10.5 running slower than Tiger 10.4 on your setup, as I have the dual processor model of the MDD as well. I've heard conflicting opinions and reports about the speed of 10.5 vs. 10.4 on the G4 class Macs, and I've been hesitant to upgrade for fear of slowing it down. I still find mine to be plenty zippy with 10.4 installed, so I definitely don't want to go slower.
As for speeding yours up, it sounds like you've done quite a bit already and have taken some necessary steps.