The frustrating part for me is that I still don't have a definitive
    reference for whether the start bit is 1.5t, 1t or 0.5t, and of what
    polarity relative to the stop bit.

The "start bit" is a bit, and needs to be one bit long.

The "stop bit" is also a bit, but you can "stretch" it, since the stop bit
is at the same voltage level as the inter-character condition ("mark",
usually.)  Since the inter-character time is not based on the bit clocks
(the definition of "asynchronous", more or less), a stop bit can be any
length of time like 1.1 bit times or 3.1416 bit times, or whatever (but it
has to be at least ONE bit time.)


    Does anyone have a pointer to an actual rs232 standard that shows these
    relationships?

This is NOT part of rs232, which is a signaling/voltage/etc sort of
standard (physical layer rather than link layer.)  You can send
non-asynchronous data using rs232 just fine (and many people do.)  What you
want is the full description of "asynchronous serial" - I suppose that
somewhere there is a spec for this (V.24, maybe?), but the usual place to
find the nitty-gritty description is in the full datasheets for some
manufacturers uart, or the app note describing a SW implementation.
Although I couldn't find one with a quick look around - the EXAR
16450-clone datasheet has a relatively nice picture in the "timing
diagrams" for receive and transmit data...

BillW