This is what I use on my Tal 200k FL 2000mm. A 100mm diameter 340mm FL achromat in a PVC pipe tube held with six nylon screws. For guidestar selection just laterally move the the magnetically mounted webcam until you find a guidestar (always works). There is no flexure as the guidescope does not move. The whole thing is very light. See pics below. Also a pic of a 'normal' telescope version.
Here is a picture produced with this guidescope and the Tal 200k
http://users.bigpond.net.au/avandonk/Car_Tal_FR.jpg
Bert