I guess it would make sense to try measuring which component is off. Are the Schwalbes further away from the 349 BSD, or the rim, or...? Just for the future. Since you seem stuck with Kenda's that are not beefy enough for you, you might as well add some (Mr. Tuffy's) tire liners to compensate. If shipping wasn't so expensive I even would have some unused ones flying around in my basement.