Did you read Kent's articles on the 'DIY mic articles up-again' thread?
I think a few people including myself want to try but the only person
I know who has tried is Ashley Stiles who is a vintage mic supremo
in England but without an Internet/email connection!
As I am away from home I don't have his number to hand but if you
type his name into a search engine you will find the articles he wrote
on tube mics for one of the recording magazines.
I'm sure he said he had a go at making a capsule.