Duck tape the Edges.

To my knowledge there isn't anything to prevent it from happening, but you shouldn't worry about it. Top sheet chipping is purely cosmetic unless it's so deep that you can see the wood core, which you should then get fixed so water doesn't get inside the ski

Ok thanks. I didn't know if it was cosmetic or if it would quickly lead to bigger problems.

The one thing you can do to limit the chipping is, using a Stanley blade, carefully trim off raggedy top sheet bits a rough bit of plastic sticking up is more likely to catch and dig an edge on the topsheet making it more likely you'll go through it into the core which will need a proper fix.

If you do get a gash on the topsheet that goes through it can be re-sealed with a dab of 2 part epoxy, which after its set you sand back to flush with the rest of the sheet.

It's a 'the nail which sticks out gets hammered' type deal.

If you're worried about top sheet chips, don't buy lines - end of story.

(Personally it doesn't bother me that much, skis are meant to be ridden hard, I've had tigersnakes and currently on the SFBs - which are the best skis I've ever ridden).