Should a stutter at the start of a sentence retain the capital letter?

When writing dialogue for characters that stammer or stutter over the first letter of the first word in their speech, should the first letter remain a capital or become lowercase when repeated?

My question is probably best explained by example...

Retaining capital letter:

"H-H-Hello," he said.

Not retaining capital letter:

"H-h-hello," he said.

Which is correct, or are both acceptable? I wasn't able to find any solid information either way so I thought a discussion could be had in the hopes of reaching a concrete conclusion.

To be entirely clear, I'm only asking about stammering over the first letter and when that first letter should be a capital.

I'd stick with the upper case letters. And that doesn't mean you need to use upper case for a stutter all the time. If the stutter starts on a lower case letter then keep it lower case. For example,

I d-don't like that. But if it was I, the I'd use I-I...

That said, I think it' a bad idea to repeat the same letter again and again. It'd be going too much over the top and your reader won't like it. I'd probably stick to a single repetition.