I was able to give this a quick test whilst waiting for my tea to brew; the sound is definitely
not the same as the RE-20...
BUT, it will cut the overall size in half, so it'll do!

(A wise man once told me,
sometimes good enough is good enough.)
The sound reminds me of the same "problem" I have with my Vulca FM vs the TX7. The Vulca FM sounds almost too high resolution compared to the original; too clean and has none of the weird colourations.
However, as this is for live use, smaller = better, and it's a much more economical use of the RV-500, as I was only using half of it. Also, it's not like the sound is
bad -- it sounds brilliant, just different than what I am used to.
So, it looks like the refinement/evolution isn't done just yet, but I'm getting close!