Well, I'm not using the MPTK because I don't have it...but I am using PT 7.3 with a 002R on a dual 1.4Ghz. processor upgraded Gigabit ethernet G4 FW400 running Tiger 10.4.11 with little or no problems and plan on upgrading to 7.4 soon. I think for me having the dual processor is key.
You might want to upgrade Tiger to 10.4.11 using th Tiger combo updater.