Tele-converters

This is actually a multiple question about a specific scenario
Firstly is a 2x Tele-converter a good idea for use with a 100-300MM zoom?

Secondly given that I would be using that lens set up with my Pentax MZ60 what would be a good choice of film for taking photos of the British GP Friday sessions from the terracing at Luffield?
Would I be right in thinking that if extremely good light and ISO 100 would be ok? Or should I be looking at 800?
I'm still a bit vague on the pros and cons of diefferent ISO for different environments

Third where would be a better place than Luffield at the Silverstone GP circuit? where would I get closest to the track with minimal fencing interference?

Depends how good the lens is to start with. You'll lose a couple of f-stops in the process. That may not be a huge problem if it's a bright sunny day but then this is Silverstone we are talking about.

If you want to avoid the fences try Stowe and Club. The spectator banks there are high enough to be able to shoot over the fences, although at Stowe you'll still be a fair distance away.

If you are going to be pushing it up to 600mm, best off having a monopod at your disposal

I'd go with that as well, I use a 2x on a 75-300mm lense, on full zoom you start to see camera shake.

I accidently left my mono at home on the weekend, and the best corner at the track was at full extension... grrr...

I use a 2x with my 100-300. But it is a pretty good Canon lens to start with - and yes, I agree entirely with Crash Test - you will almost certainly need a monopod unless it is exceptionally sunny and you can use relatively high shutter speeds.

Another thing, depending on how good your lense it, it sometimes slows down your AF a bit. Most of the time with my Nikon I wind up just manually focusing everything, that way I know what is going to come out.

I can't use AF when I use the converter.

sounds like I need to do a bit of experimenting before the big day :)

I have used a 2X telexentender with an 80-210mm lens. It works fine but expect to lose 2 stops unless in brightest daylight. Also expect some vignetting at the edges of the image as the light just cannot get in there fast enough to fill out the image. Also, a common problem with many autofocus cameras is their inability to autofocus beyond f6.0. My Canon Rebel will hunt three of four times before it can establish focus. I can't speak for other models and brands, but expect to use manual focus.

going right back to the original point, the best place from behind the barriers is up at club i've found. you can stand above the height of the fences and with my 500mm lens i got some great close shots. they're on my website just as a point of reference.

soooooooo private testing on the Friday morning at Luffiled then up the road to Club for the pre-qualifying session would be a good move?

yeah that sounds like a good plan. club's well worth it if you've got what's effectively a massive lens there.