have a look at the isabella range. I know they are expensive but we have just replaced ours after 20 years use! It has been adjusted upwards twice and still fitted perfectly. At last bought a new van and now must buy a new isabella!I think you will have to have a look at a better type of porch awning, one what has poles close to the van,
what sort of awning have you got at the moment ? if you have a look at the link below, you will be able to have a look at the specifications & weight of each awning.
Link to Jeff Bowen Awnings