@Maxwell
What you mentioned is one option, you can add properties to people at the end of the flow, and then you can create segment for all the people who have that property and use that segment to trigger the other flow. So people will get the a property at the end of your welcome flow and with that they will enter the segment and the other flow.
Possible problem here is if your welcome flow has any filters that will take people out of the flow before they finish it, so these people won’t be able to get the property at the end of the welcome flow if they are filtered out.
Another possible solution here would be to start the other flow with the same trigger just add 8 day time delay for the first email. For example if the trigger for your welcome flow is Newsletter list and the flow starts immediately and lasts 8 days, then you can use the Newsletter list as trigger for the other flow to just here the time delay before the first email would be 8 days or more if needed.
Thank you @Bobi N.
I had a similar idea but I wasn’t sure of the ramifications. With the first option you made that quite clear. I think i’ll go with the second option :)