I did a scratch build, mostly because I wanted to achieve certain goals with the design. I wanted to use a soller composites sleeve, I wanted 1/4" fins, I wanted a rounded nose cone, I wanted dual redundant computers, and I wanted the deployment charges for upper and lower events to be sized the same, and I wanted it all to be of a weight that a full J would hit ~1 mile altitude.
I had done DD so many times with my L1 rockets that, other than it being a new rocket on it's first flight, my cert launch was like any other flight for me.
As it turns out, everything worked out perfectly and I achieved my goals with that rocket.....and for the fields that I launch at, it's about the perfect 54mm motor bird for me, so it gets launched every time we go!