I don't know if it will work - but:
If both are portable, then you have the old installation in just a single folder so it should be easy to make a copy of it as backup, install the new version into the folder of the old version and then see if it worked.
And if it didn't: delete the new installation, continue to use the old one - or start from scratch with the new installation.
Here is a thread with more information about how to keep the individual settings: