Coolios, good luck with your rebuild.
Indeed, I likely overdid the tensioning on the diaphragms. I'm sure that they'll loosen over time though, since 1.4-micron mylar quickly goes into plastic deformation when subject to even moderate force.
I hope to hear how the Seikis compare to your lambdas, since I've read that they're comparable. My nooblet ears are still sailing through the multiverses of different headphone setups, and more often than not I have to listen vicariously.