I do this sort of design decision making at work. We look at the possible Failure Modes, the Effect and how Critical that is to the system. Ranking the critcality means you can then make design decision with some confidence that you know what is the most important consideration. An example would be:
Failure Mode: Float holed after collision with foreign object in water
Effect: Loss of boyancy of float (can quantify it here eg. '900lb')
Criticality: High (or give it a rank once all the other failures have been decided on).
As David says, you can treat the Criticality with operational procedures (doesn't always have to be a redesign). Then go back and compare your treatment with your mission profile and see if it still works. Then go and recheck the weight limitations you have (important to set a hard and fast not-to-exceed weight!). This might sound complex but it's essentially what you are doing but list it in a spreadhseet and record your design decisions. Helps keep track of all the ideas and ties the decisions together into a solution.
One thing to consider is how you will predict a Failure. Ie. will you notice a crack, delamination, vibration, etc before failure? If you do, then this goes in to your maintenance or pre-flight inspection checklist. If you don't get external warning, will an internal inspection be needed? If so, how and what tools/skills will you need? If you don't get much warning, maybe two sets of floats are needed. Swap out the suspect pair and take your time inspecting the old set. This means your aircraft is available for flying without the worry of sudden failures. It may mean your design can be more original and still be flown fairly often. Simplifying maintenance or having a sensible inspection process means more time flying!
I'd be happy to help out if I can.
Now - on to the fun stuff. Does anyone know if a Nieuport 17 was tested on floats? I've just moved to Pt Cook (home of Australian military aviation) and the original Pt Cook aerodrome (10min from my house) has a flying boat ramp! My brain is skipping ahead a bit here.....
