thanks for the replies. meanwhile i did it with joy2key, where i set buttons 8 and 9 (which are stick up/down) to "S" and "X". that's really all it takes, and you will be able to use paddles and stick at the same time. and most of all it doesn't interfere with H-shift mode - the additional "keyboard"-inputs are just ignored.
the problem with the profiler is: you (I?) can't assign the stick to anything, so you'd assign the paddles to "S" and "X" and within LFS the stick to shift up and down... which would delete the assignment for gears 1 & 2 in h-shift mode. apart from that it takes some time to start-up and looks resource-intense.
joy2key is pretty much straight forward. only two entries. the hardest thing was to find out which button is which.