I wasn’t thrilled with how “floppy” even Schedule 80 PVC pipe is, and I didn’t want to put a metal pole on the roof for lightning reasons.
Another solution presented itself at the hardware store: wooden mop/broom handles, which are 15/16th of an inch in diameter. That is very close to the inside diameter of a one-inch nominal Schedule 80 PVC pipe. I had to do a little sanding/shaving to make them fit, but it made the PVC much less bendy.
Yes, that works well. I used a four foot length of a wooden mop handle driven into the ground to support the mast for my Tempest. It eliminates vibration and makes it easy to take down when needed. I just slip the schedule 80 over the handle and press into the ground enough to prevent the Tempest from turning.
I should also add, this mounting system has survived 40 mph winds without difficulty.
Just to add there is no lightning risk from using a conductive pole. It’s standard everywhere. Using PVC as a matter of fact is not recommended not just for mechanical reasons but electrical as well.
When mounting conductive masts above a roof line always follow code guidelines for proper grounding and you will be fine.
You could easily make these and put them on EBay for tempest users to buy!
It looks as if Schedule 80 pipe is only available in USA, have never seen pipe that thick in the UK.
I have used this company in the UK before, and it looks like they will do sched 80 pipe if you get in touch with them: Sch80 plastic pipe and fittings (plasticpipeshop.co.uk)
For those using PVC pipe needing it to be stiffer you may want to look into filling with hydraulic cement or even a fracturing cement such as Betonamit. Not sure how well this would work but it would be an interesting experiment! 
Wood, at least in theory, should be a good choice since it eliminates vibrations and dampens swinging which otherwise leads to known problems with the rain gauge.
But the probability of your house being strike by lightning isn’t less than with a metal pole. Depending on the overall probability of being hit, depending on your location, you should consider external (and internal) protection for your house anyway.
