DimPro v1.2 may work in X3. It would need the 64bit version from SONAR 8.5 installed. Version 1.2 is DXi format so the 32bit version cannot load in 64bit SONAR. Alternately, apply the
v1.5 patch which supplies a 64bit VST format version. Version 1.5 ships with X3 Producer and probably is the best solution for new projects. It is possible to have both v1.2 and v1.5 installed and my be necessary because SONAR cannot recognize and convert DXi plug-ins to their VST counterparts. If the 64bit DXi version does not run reliably, consider installing a 32bit version of SONAR for older projects.