I don't feel this model is too heavy. And, the really light weight RC micro gear available today probably wouldn't make the model much heavier, if any.
I'm aware of the Guillows RC conversion threads for powered flight. I think some of these Guillows models are excellent candidates. I wonder if anybody has successfully converted one for slope soaring in light wind conditions. I imagine the ME-109 with its pointier and smaller nose area would be a candidate, perhaps with an increased wing area. The ME-109 400 Series kit comes to mind as it has the option to extend the wing by a rib. Perhaps the wing can even me made wider for such an application.