Extra Watts Dual mining is 27%.
R9 290 uses 45watts.
This costs (in UK) £0.10 more each day.
The extra SC (SIA) is worth £0.27 more each
Therefore, not really much reason not to Dual mine, plus there is an extra 2.5 Eth at pool each day.
Is that for one 290 card that you get £0.27 more each card? So the extract earning is £0.17 per card.
That might not worth the dual mining.
It is marginal, there is no doubt about that. But, a large number of people will mine and keep the SC in new active wallets.
They have a really good wallet and SC looks very promising for the future!
SC difficulty has gone up by 18% - since I originally posted, so daily SC is now worth £0.21 per R9 290.
It is marginally, but
of interest as an extra crypto-currency investment to accumulate.