Sol,
Yes 'Rubicon' and 'Rubicon Improved' are marmoreum seedlings. The "improved" was less of a rotter although in MA the original was fine too. It doesn't like the Pacific NW wet winter. It does have very bright color that we really don't have much of. My new 'Red Zinger' is a good red color and I have a ew seedlings from it that are redder still. These are more tectorum types but with the bright color of these marmoreums.
Like you I don't want to use a wimpy plant in crosses. Of course our wet winters are a good selective agent for killing the wimps. I don't cry over the ones that die, just saves me anguish in the long run.
Kevin