I built my own rotary and it works very well. The key for me was the home made self centring chuck. It makes a huge difference. The base is standard extrusion and some home made laser cut and 3D printed parts. The tail stock is height adjustable and can apply inward pressure on the item to avoid having to use too much clamping force. Max opening is about 110mm, but I can redesign for larger. If any one is interested I could put together a price for the printed tail stock and the chuck parts. Let me know. Certainly my parts would be less that £50. Delivered in the UK, elsewhere I could check. My intention is not to sell a whole rotary attachment, but more to help you build your own. Unless of course you would like that?