5.3: tip / cu serial communication behaviour changed since 4.10 ?

Hello,

I have diskless PCs that I connect to by serial port (using
null-modem cable). On the "master" PC I successfully use
cu or tip as follows:
   cu -l /dev/cuaa0
or
   tip sio0

----

I use to do this with FreeBSD 4.10 on my master PC. I recently
have upgraded to 5.3, and found a different behaviour of tip
and cu:

1. The bootup process over serial port used to be disconnected
    with 4.10, before and after kernel loading (each time I had
    to restart the cu command). With 5.3 this does not happen
    anymore and the boot process over serial port continues
    without any disconnections until the login prompt.
    This is a very nice improvement indeed!

2. When a long command was executed over the serial port (for
    example 'make buildworld'), I could disconnect by typing '~.`,
    while the command itself would continue; at a later stage I could
    get the command's output text by typing the cu or tip command
    again. This was 4.10 behaviour.
    However, with 5.3, when I type '~.', then cu/tip is disconnected
    but also the running command is terminated. This is rather annoying.

Regards,
Rob.