In order to use a 70" paddle effectively, you have to use a sliding stroke. This is generally only done under extreme conditions (hence the name "storm paddle"). I suggest that you make another one in the range of 84"-90". Depending on your shoulder width, the loom should be in the range of 18"-21". Holst's instructions explain how to determine the proper width.
Your current paddle is the perfect size to carry as a spare on the foredeck and to use as a storm paddle, so your efforts have not been wasted, by any means.