Really? My Q100's are about the same diameter (~105mm), and I weigh them at 2Kg (4.5 pounds). I found a user review where the owner says 1.6Kg for the YTWS-01. That is 3.2ish pounds. Maybe you were given bad info.I like the 2-speed concept, but the 2-speed Suzhou Xiongda Motor YTWS-01 has a weigth of 3.2kg, which is idiot.
In the DIY world, they had their one chance to make a splash on entry and fell on their face. Based on early user reports, reliability was poor. Some units stripped the gearing if the wheel was rolled backwards, but that was thee years ago. Lunacycle.com tried to import them to the USA, but they were selling the version with a 142mm drop-out. EIther they messed up or got shipped the wrong batch. That didn't go over too well.
Xiongda still makes it, so I suppose the production flaws were fixed.