[Remind-Fans] Need a bit of help on specifying dates

[remind at wayne47.com]

Using REMIND 03.00.24

I'm having a bit of a hard time wrapping my mind around the date
specification in remind and could use a bit of help.

At 19:30 every Friday except if that Friday is before the first
Saturday of the month.  I thought something like this would work:
   REM 6 Fri OMIT -1 AT 19:30 DURATION 4:30 MSG foo
but no luck.

Second, if I say:
   REM 15 Fri +4          MSG bar %b

I would expect rem -c1 to show "bar in 4 days" on Monday Apr 17
through "bar today" on  Friday Apr 21.   But I only get the "today"
on the 21st.

Is there some kind of "floating' event supported where if the task
is not done today, te gets rolled forward to tommorrow?