Building an aluminum kayak in this way should be do-able. Things to concider, wood-glass layup may be stiffer than aluminum, the grumman canoe has a curved shape which helps it keep its shape "flat" pannels will not be as stiff as the compound curved shape of the canoe. You may need thicker metal than used in the grumman canoes 0.060" or more may be what you end up with. this will also make welding easier and more reliable...I'm no expert on welding thin aluminum.

Bulkheads will create "hard points" on the skin of the boat which may cause cracks. I would reccomend using soft bulkheads such as foam or carefully planned and executed, formed aluminum bulkheads.

You may find building with aluminum much quicker and easier than woodwork if you have the tools and welding skills. Experiment; you can do it, and don't be afraid to fail.

Good luck with your project and keep us informed on how it goes.