Implications of ignoring permissions on external drive

My Mac Pro is in the shop and I'm working off my laptop. I have a copy of my Mac Pro boot disk on an external drive connected to the laptop.

The UID of my Mac Pro user is different than the UID on the laptop, so the ~/User/Documents (and anything else in the ~/User tree) on the external drive is not accessible from the laptop user.

I know if I check "ignore ownership" on the external drive I'll be able to access everything.

Once I get the Mac Pro back I'm going to want to clone the external drive back to the Mac Pro internal. What's going to happen with permissions? If "ignore permissions" is checked and I create files/folders on the external drive and then clone back to my Mac Pro, who is going to own (and have access) to these files/folders created via the laptop user with "ignore permissions" on the external drive?