No I didn't thin it out any. I am getting to where I've got the amount to 'center' down pretty good. I had a tendancy to over pour thinking I need more but all that leads to is a messy and costly pouroff. So far so good. When I get more time this summer when my gig is up I will try the thinner collodion to see if it pours quicker (and as the summer heats up I think that may become important) but right now I'm just using up some old collodion that needs to get used before getting too old.
Have a great first giant plate. They are fun. Bellows extension is a mofo though so unless your doing an infinity shot get ready for some long exposures!