I've seen some talk about this, but no clear answers.

I have a glidecam and I need to put a quick release plate on it. I've seen a couple manfrottos that are different sizes, and i'm wondering if either of them will match my davis and sanford quick release? I think it's an FM18. I am pretty sure that when I had a redrock M2 film converter it was the same plate as what come with the converter.

I took the D&S plate to a local camera shop and tried it in one of their manfrotto heads and it was a little too big - but i was reading that the 357 is slightly bigger than the 577? so maybe they match? any ideas?