Installing gas logs, plumbing question

I am hooking up a new set of LP gas logs in my wood burning fireplace. I had the plumber install a gas line to the fireplace when we built the home 2 years ago and it has a "keyed" shut off valve mounted in the side wall. To be safe, I installed a secondary 1/2" -> 3/8" T-valve with a flared connector where the line comes inside the fireplace for quick access. The line inside the firebox originally had a 3" nipple and a cap, but I replaced this with a 1" nipple to ensuse room for the gas log appliance. There are are no leaks to the new T valve using the soapy water test.
Next, I installed a flex line from the T-valve's flare connector to another flare connector on the logs. When I turned gas on at the new T-valve I saw a very small trace of bubbling between it's flare connector and the flex tubing and directly turned the valve off. The flex tube is as tight as is it will go onto the connector, and I did not use any pipe compound per instructions on the flex tubing.
Can I simply apply some pipe compound to the threads on the flare connector? Or, do I need to replace the T-valve and/or tubing:?
The flex tubing came with two 1/2" -> 3/8" flared couplers, so I could possibly replace the flared shut off valve a 1/2" -> 1/2" non flared T valve.
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Never had a flared fitting leak. Is your new valve rated for the heat that it will experience? I used a key valve outside my gas fire place and stubbed into the fire box with black iron. I connected directly to the black iron and covered everything up with the vermiculite after leak checking.
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Didn't think about the temp. rating on the valve. Just prior to reading you email, I read about a stainless steel flex hose that was black coated for visability and heat protection to 350F.
I used a gas dryer T valve and 3/8" flex hose from Lowes that said it was rated for alternate uses such as high BTU gas logs. For this reason I didn't think about high temps.
I can pull the valve and re-install the original 3" nipple with a 1/2" -> 3/8" flare adapter and just use the outside key valve, no problem. The log installation instructions showed a T valve, and I thought that in the case of an emergency, it would be easier to shut the gas off directly at the T and not have to hunt around for the key.
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