spitfire header gasket question

I started my apprenticeship, and all I did for 5 yrs, was oil changes, brakes, 2 to 4 bbl changes, 3/4 race cams, 4:11 gears, and headers, headers headers .
After mosta the first 6 sets leaked like hell, customers bitches, my mentor showed me how to fair the header flange by welding up the valleys and filing down the hills of flange weld.
Back then the assembly welding including flange was by hand, and not planed true flat, like these days.but even now, they are not always true !
I never let a job leave with a leak, if it started to leak later, I removed and re-draw filed the weld on it, no charge.
I have checked true, and draw filed every set since, dozens and dozens of sets, all makes .
Need a 1/8 inch clearance at a pipe, file the flange !
I always use the gaskets sets supplied or plain Mr Gaskets on every job, never even seen a Remset .
Do it once,
I was fortunate to have a fabulous mentor, he and partner were chosen to compete in the " Plymouth Challenge" placed top 3 iirc.
Thank-you Ed Leippi, Victoria B.C.
Cheers .