I think lighting is way overrated. Unless you want straight mushrooms, that grow straight up, don't worry about it. Burple's right, in that they need light in order to know which way to grow, but having them grow every which way never bothered me.as for them needing light to pin, that's not always true. try it without light, if you can't get them to pin, just stick a little flashlight in there with them for about an hour or so a day. i never had a problem with them not pinning because of light.
good luck, and don't stress over the 'light' stuff 
Link
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Remember a Day Before Today
A Day When We Were Young
Why Can't We Play Today?
Why Can't We Stay That Way?
-Pink Floyd