Parameter Footswitch for EDP

["Bernhard Wagner" <loopdelightml@nosuch.biz>]

I own a blackface EDP and would like to add a Parameter Button to my Pedal.
I managed to reconstruct all functions
Record Overdub Multiply Insert Mute Undo NextLoop
with the help of:
http://loopersdelight.com/tools/echoplex/echopedals.html

except Parameters.

I tried both 28.0k and 33.2k and also some tweaking with a potentiometer 
but
didn't get it to work reliably. Often I'd get Overdub instead of 
Parameters.

Has anyone succeeded?

THX
Bernhard