Congratulations on a very well analyzed trade...good work.
Since the USDCAD
is in a Daily downtrend, finding a double top is a compelling signal since it is signaling an entry in the direction of the Daily trend...a higher probability way to trade.
Yes...12 days would be enough time. If the amount of time were longer, that would even be better. The more time that elapses between the occurrence of the first and the second top/bottom, the stronger the signal will be.
24 pips of difference on a Daily chart is definitely close enough to qualify as a double top.
Below is a link to the Daily FX site. It will take you to the Instructor's Trading Tips area and a brief article on determining profit targets based on double top/bottom patterns. Scroll down a bit after you open the link and you will come to the article...