I have found this dynamic spine calculator very helpful
http://heilakka.com/stumiller/I use Easton powerflyte 500's , 50 grain muzzy brass incert, 125 gr point, 3 5" feathers for my 44# recurve and 45# Tradtech Pinnacle with deflex reflex limbs. They shoot very well. I'd bet 400's would be too stiff unless you bumped the FOC right up. Check it on the spine calculator - it's amazingly accurate.
I bought a set of Gold Tip Traditional 600's for my 34# recurve 125 gr points 30 gr alloy incert , 3 $.5" feathers. They are a very tough durable shaft so I'd say the stiffer spines would be equally as tough
regards Jacko