I too noticed that message before I purchased them - so I called Dormont directly (the manufacturer of the hoses). I told them exactly what I intended to use them for - plumbing propane to three burners and probably around 10psi for each up to 30psi (but this shouldn't really happen on a single burner). They said it should be no problem as each of these hoses is pressure tested to 100psi (to meet CSA guidelines they have to far exceed the rating). They said they have to rate them at 1/2psi because typically these are installed at homes in NG applications and if that is exceeded you won't pass inspection or meet CSA guildlines. Obviously, we're not trying to do either
The only time I've had a problem with leaking is when I was an idiot and didn't read the label which tells you do NOT tape the joints where the hose connects to. Otherwise it's been fine.
Those Brasscraft flex connectors from Home Depot are rated exactly the same BTW - 1/2 psi. Check it out in the details here:
http://www.homedepot.com/h_d1/N-5yc...splay?langId=-1&storeId=10051&catalogId=10053.