Can a June 2003 MDD PowerMac G4 upgraded with a 1.42 DP still boot into OS 9?

I have a PowerMac G4 MDD. It's the very last G4 Apple produced and also happens to be able to boot OS 9. It came with a Single 1.25GHz G4 CPU by default or you could get a 1.25 DP option as a build to order option.

I know you can take the 1.42 DP from the previous PowerMac G4 MDD and put it in this model, and it will work with OS X. What I don't know however is if the machine will continue to be able to boot OS 9?

I know the 1.42 DP is from a Mac that cannot boot OS 9 but I'm I'm wondering if that limitation is due to the logicboard rather than the CPU. Has anyone ever actually performed this upgrade and successfully booted into OS 9?