My fully clad weight is similar to yours. I use the blue and yellow elastomer pieces in the top chambers, and my stem is 100 mm. Necessary to mention I
only use two pieces because I also have Innerbarends, and my riding position is far forward, making the weight on the long stem similar to what a drop bar would have gotten from me. I feel you should try a single blue elastomer piece in one of the top chambers only. (I used that before installing Innerbarends). Your riding sensation should be like "flowing" over harsh terrain, and you should feel your e-bike frame as if it were breaking
Please experiment a little. The RS ShockStop stem is indeed very good but it should be optimized.
Now, I can understand the Varia is the priority for you. Yes, please do as you intend! The combination of RS SS front/rear is a beautiful experience provided both items are carefully tuned in.
Besides, what is the tyre inflation pressure of yours?
