The idea had been clanking around in my noggin for a long time. Its nothing new or original: a short longboard. In this case, 6' 6" x 21" x 3". It was originally designed to be 22 or 23 inches wide, but once I started cutting the template, I went with 21 because the others just didn't look right to me.
At 6-6 its not really a longboard, but I wanted it to have obvious design elements of a longboard, and hopefully, to ride similar, i.e. (not really a "noserider" per se but) a glide and trim board (maybe a cheater 5 now and then).
I wanted to incorporate some of the elements of my favorite longboard, and add a few things I haven't tried yet.
The planshape was originally drawn as a quad, going the other way, and I was looking at it thinking I could reverse it for a single-fin mini-longboard shape. Then I saw the Brom Stepchild, and I'm like Yep, this could definitely work as a short longboard.
I still want to build the one going the other way, so I would have two boards with identical planshapes, but going opposite directions - hence the term Stepsister. Cinderella had two ugly stepsisters, and she wore the glass slipper. I can't surf the glass slippers at my age, but I might make out OK with the ugly stepsisters. With the funny-looking stepdeck, I'm thinking of calling this one the deck blister stepsister. =)
I finished a hws stepdeck awhile back, and was unhappy with the way it rode. It was 6-6 also, but 23" wide, and the stepdeck and rocker were more extreme. It was ok to paddle, but riding, it felt way too floaty/corky, and very awkward to ride. So I toned this one down a bit. I still went with a stepdeck for increasing volume, but not so extreme as my hws, and only 21" wide this time. I'm also giving it a deck concave, which gets more pronounced toward the back, after reading Harris' and others' comments in that thread.
I want to put a Thrailkill double single-fin, I have no clue as to the explanation for them, other than that they look really cool to me. And I like trying new stuff, and the boards I've seen them on have gotten good reviews.
I cut it out of an old Eco-tech longboard blank, so I had boatloads of foam to play with. (I've got one more after this to use up, then I give myself permission to buy a modern blank) I started by cutting about 3' off the blank. When I started cutting the outline, the blank fell completely apart at the stringer, so I had to glue and clamp it. It seems fine now.