I have two Yamaha 2000's, about 50lbs each. I typically use one while docking, but sometimes two are needed if it the temperature gets too hot or too cold. I keep them in the truck bed unless they're in use, and have a heavy gauge anchor chain and disc lock securing them (through their plastic handles, haha.)
I don't expect the chain to do much against someone determined. It's only for insurance purposes. When I file a police report, I can document that I took reasonable effort to secure my property.