With due respect, Poles, you might be overdoing it. You may just start with an arbitrary version (let's call it R4 for now after mmontuori, krystianp and Z versions), then comes all experimental versions (R4X1, R4X2, ...), then last experimental, once stable, becomes R5. In between Rn and Rn+1, work is done only on one issue at a time. That way, everyone would know that an X in name means untested and which version fixed what. My 2˘.