Plastic corrugated sheeting for covering raised beds

Hi

Last week I felt really smug with myself.  I went out and purchased some plastic corrugated sheeting to go over my raised bed.  It would a) help to warm the soil b) keep the cats/birds off and c) help to provide some sheltered growing for my winter lettuces and hardy spring onions.  I had the sheets raised slightly on bricks around the edge with more bricks on top to hold it down.  All going well.

Until the rain last night that is.  The weight of the water just forced the plastic to buckle.  It hasn't broken it or anything but I guess I'm going to have to drill some drainage holes to prevent this happening again.

Does anyone else use plastic corrugated sheeting in this way?  What are your experiences please?

OG

Good thought...I'll have to fish out some more bricks from somewhere and work out how to stop it sliding off at the other end.

Thanks