It is not advisable to use multi-boot AT ALL as the possibility is that you mix and match versions of different kernels and Enigmas, which can lead to instability of you STB. The current way multiboot works is unreliable because of the way it is implemented: it only loads a different version of Enigma and not the correctly associated kernel. If the kernel in flash is a different version than that required by the image in multi-boot, results will be unpredictable. The OpenPli team is looking at the possibility of creating a proper multiboot (first stage loader replacement), but this is still a long way off as it is not an urgent requirement and is a background task.
So my advice is, choose a good image and stick with it. In my opinion the best ones out there are Gemini, OpenPli and Nabilo in no specific order. My first choice is OpenPli for the Dm600 as it has a very nice 7 day EPG and is stable.