I have built both versions of the Wee Lassie, but from the Featherlight book. I am not sure how or if the Newfound versions differ, the lengths and widths you quote are the same as those in the book.
My wife uses the shorter version often for a trout fishing platform on Sierra lakes and loves it. The short one has a good deal of rocker and is quite easy to turn. I found that the longer one, as built from the plans in the book, has a nearly straight keel and handles much differently. So much so that I modified the forms and have now nearly finished a second long one with an inch or so of additional rocker.