Thanks for the feedback.
Looks bit tricky with supports attached to custom dummy legs. Default actual symbol 01HG is blank for dummy legs, and dummy leg is described in PCF as pipe.
When we force to use custom symbol for dummy legs and suppress pipe definition in PCF for this support, dummy leg appears as symbol. In default case when pipe is used, the dummy leg is represented as a pipe with certain length.
To my regret I do not know how to create custom symbol with variable length. and it seems that there is a part of hard code involved as well.
Regards,
Artiom