New polytunnel advice!

So. I'm purchasing a 6 metre polytunnel from eBay for £109 which includes a cover. I already have a lot of plastic sheeting which is uv resistant. Do you think it would be wise to place the plastic sheeting over the cover that comes supplied with the polytunnel in order to prolong the life of the cover already supplied, or would it just cause more problems? Any advice would be greatly appreciated!

Carl ☺