Revel Propulsion, a company in OR, has a DIY mid-drive with a bottom bracket incorporating a torque sensor. I procured a kit and it is designed and executed masterfully. The motor/controller, display and all mounting hardware weigh slightly less than eight pounds and will replace the bottom bracket and crankset which weigh slightly more than two pounds. The battery and "cradle" which mount on the downtube weigh slightly more than four pounds providing a net addition of about 10 pounds. The torque is reported as slightly greater than 60nm making it in line if slightly less than many mid-drives, but this kit has been designed for individuals who like to pedal. I am not affiliated with the company in any way, and will report on the kit at some future time when several other projects are completed.