cannot specify project_dir-relative path for Tomcat Home?

pertains to intellij ultimate latest ga:

my understanding is that all paths specified within a project are project_dir-relative (and thus portable). I was trying to define a project_dir relative 'tomcat home' in run configs > application servers > tomcat. but:

1) specifying a relative path results in Intellij IDEA bin path being prepended

2) starting with $PROJECT_DIR$ explicitly is same as 1)

3) setting an absolute path persists across computers.

How can i specify a portable tomcat home path?

for context: though inelegant, we found it useful to keep tomcat binary in our project SVN Trunk, under $trunk/some/path/tomcat ($trunk is also project home dir)

thank you,

-nikita