Sorry for the delay, I sort of lost the thread.
My canvas is heavy ex army rip stop tent material.
I think Robin and the crew have assessed it and ruled it too heavy for the frame as is.
I have, however, got hold of some used scaffold sheeting material which is translucent and rip stop.
It might do the trick.
I was thinking, only theis afternoon, that I might drag it up t'Pit and see if anyone would like to make use of it.
A can or two of Guinness (I appear to have a medical issue with real ale these days.) would be welcome in exchange for my effort in scrounging and transporting the stuff.