Why do serial load GUI thing for Basic when you would be better off installing an M7762 and a RL drive or at least a set of RX drives and going with an operating system like RT-11 or RSX-11? Loading Basic or any of the other utilities from a disk is easy and fast with an OS and that hardware is more then up to the task. Loading Basic in RT-11 is easy, just type basic at the prompt and it runs, and may ask what features you want and the like but no issues like you are having now. This is all speculation on my part so people are probably going to get pissed but systems like the 11/05 and 11/10 were early examples with limited capabilities and maybe at best suited for loading a simple assembly language program via the con but when you get to the heavy weight systems like the 11/40 they were intended to work with large drives, complex operating systems and in most cases multipole users.
RT-11 SJ (Signal Job) only requires 8K with its monitor only using 2K so you can go with the 16K that you have. If you build out to 32K you can also run the FB and XM monitors in RT-11, with the XM (Extended Memory) you can address up to 124K of memory. Your 11/40 is like a car and trying to load an assembly version of Basic is treating it like a lawn mower. Nothing wrong with doing things in progressive steps but somehow I feel that what your doing is like trying to load cassette basic on a PC, and when you were dealing with a IBM 5150 that was state of the art but your 11/40 is at least a 486 if not a P1 by comparison. I know you have the skills and the hardware around there to do this and just to prove that I am not a complete jerk in saying this I would be willing to pull a drive, cable and controller card and come up there and help you sort thru your stuff and get the system going with an RL drive. Just a question of finding the time or you can drag down a drive and card and I have systems that we can test it on.