Hi
This job is not as bad as it looks if you cheat a bit:
With roof on, lift the roof to the up position
Remove old canvas and all fixings apart from support bars (leave staples in plastic strips)
Find centre and fit lower canvas all of the way around with the metal fixing strip.(make sure you have the canvas the correct way around - mesh on outside)
Start stapling the top at the rear in the centre, pull tight as you can, work out to the sprung arms
Leave enough fabric to go into the corners and start on the sides
Do sides first then work on the front, there may be a pleat due to extra fabric, but this can't be seen from the outside.
Double over fabric and staple again
Then go back to where the arms are, remove one at a time and support with a piece of wood, staple fabric and refit arms
Tap plastic strips back down and refit fixings.
I have fitted about 10 in this way and they are all still fine, I can fit one for you for £50 if you don't want to have a go yourself.
Jon