Mash hopping

I'm brewing an ale tomorrow based on the Janet's Brown recipe, a cracking beer that I've tasted but never made.
I'm going to try mash hopping instead of dry hopping. With this method you add the hops to the mash and remove them before the boil. This should add a lot of flavour with no bittering.
You would expect the flavour to disapear during the boil but I understand that it doesn't. I'm adding 20g of Northern Brewer and 30g of Centennial.
To do a proper experiment I'd need to split the batch but I can't be bothered. I don't know if it'll work but I'm sure the beer will be good either way. If it doesn't I'll give it to my mate who'll drink anything.
Does anybody have any experience of this method? If so, how did it turn out?

Never tried it, but I would be interested in how it comes out.

It added a lot of aroma but no bitterness before the boil which is what I was aiming for but it was impossible to tell if it survived the boil as I added Northern Brewer for bittering. I would guess it did. I'll report back on the finished beer.
I'm  using the Mangrove Jack's Liberty Bell yeast which I've read is the Anchor Liberty strain. It finishes higher than US-05 and should give me a maltier beer. It took off in about 12 hours.

I'll report back on the finished beer.

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Cool.