I had just got off the phone with Lambretta Works and was absolutely thrilled to hear they still offer their "XP tuning" for D/LD cylinders. Yup, I was grinning from ear to ear until I DROPPED THE CYLINDER.
Two fins broken!!
It's at the welders right now and I'll know soon if they can fix it. Cast iron is a bit of a pig-in-a-poke: you never quite know what they put in the mix. At least the welder sounded hopeful.
I got it back from the welders today and it looks perfect. Other than a lingering ringing in my ears from bashing my head against the wall, all is well!