I can gleefully report that TotalFinder v1.7.1 beta is up and running on my El Capitan beta 5 installation on my Fusion Drive. Yippie!
For reasons undetermined, the Recovery HD created with El Capitan beta 5 did not include the security command to disable SIP. I spent hours and hours downloading this and that, trying many suggestions from other website bloggers. But then I was put onto the following.
On the Apple Developers website (Disable SIP using Terminal command.) are directions how to disable SIP using the /usr/bin/csrutil disable in Terminal. This is a great option for those who have discovered that your beta 5 installation removed the Security option under Utilities. Check it out.
BTW: Did I mention that I am gleeful? giddy? smiling?