An explanation is always a good idea, because the main use of SCO's is to give the seller an option if th first buyer backs out.
Sellers are not able to determine with certainty that the first buyer has backed out for a minimum of 6 days, so explaining that you have extra pieces tells the buyer WHY you are sending the offer so quick.
Imagination will often carry us to worlds that never were. But without it we go nowhere. Carl Sagan
