After days of frustration I finally found a way to install High Sierra from the USB.
Booting the USB, selecting Install icon at the new Clover screen, on reboot selecting the install icon for the HDD was getting me a white screen, then the eternal beach ball. One go-round looked as if was going to work but then a message popped up that part of the installer was missing or corrupt and HS could not be installed - reboot and try again. Did that and was back to white screen with beachball.
Finally thought to try something different. If the installation files are on the HDD after the first installation pass, why not go ahead, boot Sierra, install Clover to the ESP of the HighSierra drive, copy over the RTL8111 kext for my network NIC and the new FakeSMC.kext and replace Clover installer's config.plist with my Sierra one and then shutdown, disconnect all drives except the HS one and reboot?
Did this and it worked like a champ - 15 minutes later I am typing this from the new High Sierra Public Beta running on my sig build.
Going to try it again, this time installing Clover with FakeSMC, network and config.plist to the drive first, then run the first install with USB installer and at reboot remove the USB and let it boot from the HDD and see what happens. Will post results.