Which 1.4 teleconverter for Sigma 50-500 w/Canon? (1 Viewer)

I know this has been asked before and I have trolled through all of the posts that look like they might have the answer, but can't find it. So here goes:
I have a Canon 20D utilizing my Sigma 50-500mm EX DG HSM lens. I would like to be able to put a 1.4 converter on it and have autofocus on bright sunny days (we get a lot of those here in Arizona). I currently have the TAMRON SP AF Tele-converter. I have taped the 3 pins on the left side as I look at the lens side of the converter. Can't get autofocus at all. I am using plain clear scotch tape. Is that the correct tape to use? Do I need to use a different teleconverter? Or should I just give up?
Since my better half has just shot down my getting a prime lens - I''m going to have this lens for a while as my primary birding lens. And don't get me wrong it is very nice and works very well. But I would like to get a bit more distance from it.
Any help is appreciated.

I think that with the 50-500 you will need to rely on manual focus if you add a 1.4x tc, I know others who have tried it with the pin taping trick but it doesn't seem to work.

Thanks, that's what I was afraid of. Just have to trust my trifocals a little!

I have owned the same camera/ lens combination and have tried both Sigma 1.4x and Jessops 2x converters with it. Even by taping the pins I found that autofocus worked only about 10% of the time in good light and that involved a lot of "hunting". Manual focus is a much more reliable method.

Thanks, sandpiper. Unfortunately with my eyesight that is extremely difficult. Hey, at least it's a digital and I can just trash the bad ones instead of spending money on the prints!

Lisa W said:

Thanks, sandpiper. Unfortunately with my eyesight that is extremely difficult. Hey, at least it's a digital and I can just trash the bad ones instead of spending money on the prints!

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I've tried the 50-500 with both 1.4 and 2X, what can I say? Put it this way, I no longer own the converters!
Neither provided good images under any conditions. It just pushes the 50-500mm too far. I love the Bigma, it's just not suitable to use with converters, at least in the test I did anyway!