I've found going up one size is enough in swimsuits unless you are trying Miracle suits, which tend to run smaller and need to be sized up two sizes. The only consideration you might want to factor in is length. I recently ordered a couple of suits from Lands End in my normal swimsuit size (one up from my normal clothing size) and the length was far too short....I needed a long torso, although I'm pretty well-proportioned.
I think your plan to order a bunch of sizes is a wise one...just make sure to order a few long torsos for comparison.