FCPX workflow with older project

Hi guys,

I have an important issue and hope you can help.

I am taking a feature length project from a director who has edited the rough cut of the film with FCPX version 10.0.8. He has worked on a mac with the following specs:

2009, 2.93 Ghz Intel Core 2 Duo, 8 Gb, 10.6.8 OS Macbook pro

He asked me to help with the edit till the final cut, but eventually he wants to be able to work on the FCPX again at the end of the process.

I have a more recent system, a Macbook pro Retina, 2015, Yosemite, Version 10.10.5 and my own version of FCPX is a 10.2.2.

I am a newbie with FPCX, since I use mostly Premiere and Avid so I am not sure what to do .

What do you think is the best workflow here in order to be able to go back and forth with the director considering he wants to be able to keep editing himself after I am done?

Do you know a simple way to do this? I also though to install that previous version of FCPX 10.0.8 he has, but it seems that Yosemite has issue with that, so it will not work. At the same time, if I upgrade his project, then he will not be able to edit himself afterwards, since his computer is too old for version 10.2.2.

I am stuck here, and don’t know what to do.

Could you please help and advice?

Thank you so much,

Chiara

Use XML instead of sharing the project?