Thanks to Ian Hammond, Lou Ernst, Malcolm Macloud, and Jack Rubin,
In addition, I've added the CAPS11 bootstrap into the emulator module, so no more toggle-in required.
Lou Ernst reported that RT11 V5 does not work with the TA11, even on real hardware. The simulated TA11 does work under RT11 V4; it's included in the stock FB monitor.
One anomaly with RT11 V4 - after writing files to CT0: and then doing a DIRECTORY, all the files lengths are 0. The files are there. I can type them and DIFF them against their source.