Here's the thing - the optical system is only as good as its weakest link. I'd hate for that to be a major optical component such as the secondary. Stick with a good name brand like Galaxy or Protostar. Others will chime in with those they've had good luck with I'm sure.

I'd be interested to know how the quartz ones perform as well. I don't think they're common in the size I need for my project, and are quite a bit more expensive. Still, I'd be interested to know what their advantages are besides thermal stability.

I hope you're enjoying your telekit project. Have you actually received it yet? I did a 15" f/5 Telekit a few years back. Love it. I also used Randy for the secondary holder and spider for my current DIY. If you've got any questions as you go along with the telekit, let me know I'll be glad to help. Randy is quite accessible too, and his instructions are very good, so you may not need me, but I'm here if you do.

-Brian