Infrared Photography with Filter; Cokin P-Filter or Direct Mount?

I want to play with infrared, do have a tripod, I don't have a problem with long exposures (actually I kinda like it), and I'm fine with focusing before attaching it. So if there is a big reason why a filter won't give good infrared pictures oppose to a dedicated camera besides those, I'd like to know, but those are the reasons I keep hearing thrown about most of the time.

That said, I wanted to get some feedback as to whether I should buy the Cokin p-series infrared filter or a different kind that screws directly on - such as Hoya (though I'd rather not spend $150 on some goofing around). I have heard one person worry about light coming in with Cokin, I don't know if that is a problem, if anyone has experience with using that filter, or if taking some of that photography tape (forget the name) around the edge solves that concern.

Cheers

Hmmm this is the second thread I've responded to about IR today......it seems perhaps IR remains not that popular. Anyway, here goes: The screw in filters are the best and yes the reason is 'light leak'....I have a Cokin filter set and wouldn't bother doing IR with it. I have a converted camera. However that being said, there are some desirable effects from long exposure IR.....I'm thinking windswept skies in particular.

Go with the thread-in filters. But what's more, go with the cheapest Chinese imports you can get off Ebay. I've shot with cheap ones as well as expensive Hoyas and while there are some differences, for the most part they won't show up in the resulting image.

Also, a word of warning. When shooting with my pre-converted XTi, I easily got good exposures with a 10-20 second shutter speed at ISO 400 in good daylight. When The Wife got a 50D, I tried the same, but the hot mirror in that model was so aggressive that shutter speeds of 30 seconds and up were necessary. I haven't tried shooting IR with my 7D since I've had the XTi converted, but I suspect its hot mirror is even more aggressive than the 50D. Canon does not like non-visible light!

I went with the Cokin filter set just because I am not about to spend 500 to buy a camera and convert it, plus the Cokin filter set gives me quite a bit of flexibility. I have not used it too much so I am still seeing how good the results are but they do not seem to be too bad.

For anyone else interested, yes, the Canon 7D cannot do infrared. The hot mirror is far too effective, I tried everything but it just doesn't work. I am currently using my old Digital Rebel for infrared, but I think some of the pixels have died so I need to find some other cheap body for that (maybe a 5D).