Maybe its just the picture, but to me it looks more like it has well rounded corners than trapped. Trapping should reduce weight because you have less area under tension which reduces resistance to bending. I have only ever trapped two bows. On both I trapped one fourth of the width from each edge in towards the middle. This reduces the outer surface area of the back by one half. I don't know if thats the proper way to do it but it worked for me.