I just purchased an older 13' Avon with the same thing. I needed the space for an agile bowman for conducting rescue work on the river. To remove it, get a heat gun and apply some heat but don't get it too hot. Low heat over time is the key. You should be able to get a corner so peel somewhere. Be very gentle around any seam tape that is used on the main tubes running the opposite direction. Toluol is another tool that can help. As the rubber is peeling up, take a small brush with just a little bit of Toluol on it and swipe at the underside while under a little pressure. Be careful with Toluol around other seams as well. Any residue from the cover can be removed with a nylon brush wheel and a steady hand. Good luck.
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