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If I were you, I would use aluminum trim coil over the siding and get it out on the ice to fish. The season is too short as it is and to do a major overhaul of your shanty during prime fish time is probably not what you want to be doing. Aluminum trim coil is cheap, light and durable.
If it were me, I would get that out on the lake and be using it! Upgrades/repairs are for off-season in my mind, unless they're necessary. Nice score on the shack!