Hello drdann,
custom installer says it all. You will have to build your own custom installer by following
this procedure
On the other hand Shura1oplot, over at
TheEbook.org, has shortly posted links to his nightly-build. You may try these.
As you already have PRS+ dl the zip-file, extract it to your PC/Mac, copy the whole folder PRSPInstaller to the root of your device. Shutdown, restart.