Changing release version on source

[Mike Jakubik]

Does anyone know how to change the release version of the source code? I 
have some brain dead software (Plesk) that insists on FreeBSD 5.3, while 
it will work just fine on 5.5 and even 6. I am wondering i can change 
the version of RELENG_5 code so that this software will think its 5.3-R 
and let me install. I have tried changing the variable in 
/usr/src/release/Makefile, but that seems to have no effect.