Zip Dee will cut them to length. You can definitely install an awning, but it's not the easiest task. This is a fairly comprehensive thread
on variations in how to do it. Pay attention to post #10. I have had professional installers also say they think the rollers come a tad long. If you decide to go ahead, you might call Zip Dee and discuss this issue with them.
I would definitely reinforce the attachment locations if you can get at the inside of the shell.
Here is a link to the original instructions
, which tells you about the spring in the roller.
Sometimes the roller or arms can get jammed by sand. Getting the awning operational
can result in other problems. You can also repair a roller
if the fabric separates from the tube slot.