All the ST programs on that link (that use the serial interface) are pretty much useless...they require you to simply 'print' (using gem print command after clicking on a file) the file you want to send to the portfolio across the serial port as a binary file and try and catch it on the portfolio using the (crap) copy command! You cannot send anything back to the Atari for backing up etc.
As for ST-trans, I havent tried that...i will search for a copy...but i wondered whether there was any falcon specific programs that made use of the 9-pin second serial port that the falcon has (but ST doesn't). I have a printer plugged in to the first port already on my faclon (which obviously i could remove if a program doesnt exist!!)