Helicopter Sound effects

[SayethWhaaaa 245]

I've been playing around with some sound bytes, effects, audio recordings etc because I'm looking to customise some of the helicopter engine effects. I've recorded and kept a few that I like and use with some of the choppers in my current installation. But I was curious as to what the limits to the sound loops are. ie, is there a file size that's too big, or a loop length that's too long etc?

Also, are there any issues (say, copyright for example) with posting sound effects as I've been bitten in the ass once when using generic samples once and people can get pretty tetchy with effects since they can sound similar to a lot of other effects.