Some of the slow deltas in this video span 40 inches, and some 30. This link has some photos with measurements of the 40-inch span version at the end of the video. Not all of the lower skids are needed; only the center and outboards. Scale it to 30 span for the smaller one. The 30 size uses a 2730-1500kv (100 watt) motor with an 8/4.3 or 9/4.7 on 2 or 3S 500-800mAh LiPo. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-2sY8xjIjq3I.html