RTV, Hylomar... a preference??? Have both. I used a bit of the Aviation sealant when slapping on the cam cover. The excess cleaned up nicely with denatured alcohol. Brent is correct though, those cover rubber gaskets are not as "robust" as the Honda original.
Here is a new addition. For those with Mac cans, for less than $130 or so, it's a great replacement. I cannot comment about performance differences, but the sound is much throatier. I doubt if much of any performance difference, if any.