I have been a bit quick in saying that Odo DrFusion2 was alright in Reaper (or maybe it is the new version with enhanced midi ?) :
yes, it works, but it slows everything a lot !
engaging / disabling the plugin takes more than 5 seconds, recording does not start immediatly...
Well, still not perfect !
edit : confirmed. Odo DrFusion makes Reaper be veeeeerrrrrry slow, and it crashed two times tonight.
It's such a pity, i love that drumsynth...