Potjoe

Absolutely. As long as you do not open a document in 3.x, they are still usable in 2.x. I was working on several documents in 2.15, and I was still able to open them after going to 3.8 then going back to 2.15. Actually, there is a message "Unable to display the document please upgrade the software" in every notebook you opened or created in 3.x. So indeed, conversion is on a per document basis and not a batch process at boot.

However, as you stated, it's still a rather unsafe situation as any miss click in 3.x will definitely make your document unusable in 2.x.

Just to let you know, I was still able as expected to open 2.15 files in 3.8, but sure, once flipping to 2.15 again, the file cannot be open anymore since they are converted when first opened in 3.x

Actually this is the issue. New firmware is always written to the inactive partition. Thus, if I update from 3.3, it will overwrite the 2.15 inactive partition with the new 3.8. The solution have been given by rmhack : using RCU, you can upload a firmware to the inactive partition.

I will test to create a notebook in 2.15 and to open it in 3.8, to see if the conversion is still working. I'll let you know

Thank you very much for your warning, which should be read carefully to any unadvised user. However, I already had experience with switching back and forth between 2.15 and 3.x. indeed it is really important to back up the files using RCU before trying this.

Actually, this setup is doable safely as long as it is strictly for test purposes, and not a durable solution. Indeed, you're not right when you say :

"The first time 3.0 boots up after being installed, if it finds any .lines files from 2.x, it will convert them to a directory full of 3.x format .rm files. Once this happens, if you were to reboot into the 2.x software, it wouldn't be able to read the pen stroke files."

Because file format conversion is not started when booting the device in 3.x, but when you open for the first time a file or notebook in 3.x, and convert only this file. Thus, for test purposes as I want to, you can create a notebook to use exclusively in 3.x : it will not be compatible in 2.15, but as long as you do not open any other file, you're ok.

Thank you for the insight! It's really tempting. Do you know how I should proceed to update to 3.8 and to keep the possibility to roll back if I don't like it ?

Yes it was my point. I would like to test 3.8 + rmHacks setup and to not lose the ability to roll back to 2.15 if I don't like it. What are the steps to update to 3.8 while not loosing the 2.15 partition ?

I think I'm loosing the ability to switch between documents with finger swipe and bookmarks, which I found myself using really often. Last time I checked, I hated infinite scrolling, so not sure about that. And, I'm not sure that I'll be able to get used to the new page button..