There is no need to compile 2 mod_lisp versions. Why don't you just change the LispServer directive, as shown by Edi in a previous email ?
LispServer2 127.0.0.1 3001 "tbnl" => LispServer 127.0.0.1 3001 "tbnl"
Indeed, that works fine. We must have botched something when we tried that the first time.