Harness is a pluggable heterogeneous Distributed Virtual Machine (DVM) environment for parallel and distributed scientific computing. This paper describes recent improvements in the Harness kernel design. By using a lightweight approach and moving previously integrated system services into software modules, the software becomes more versatile and adaptable. This paper outlines these changes and explains the major Harness kernel components in more detail. A short overview is given of ongoing efforts in integrating RMIX, a dynamic heterogeneous reconfigurable communication framework, into the Harness environment as a new plug-in software module. We describe the overall impact of these changes and how they relate to other ongoing work.