I shot The Asia pacific Masters games with 4 other photographers who all do/did event photography. at first money and payment was a bit of a sticking point. I had 600/4 which enabled me to get into more sports so to speak which meant, (to me anyway) I was going to sell the majority of images as I was the more experienced sports photographer having shot every type of sport for the last 5 years, However all the photogs brought something different to the team and contibuted equally to the success of the event. We simply sent people to sports which suited the gear they had.
We ended up selling something like 20K worth of shots from memory. We split the sales evenly with the games organisers taking 15%. It wasn't as profitable as I had hoped given that I wanted a split of sales on who shot the pic gets the money. If it had been like that I think I would have ended up with atleast 40% of the sales.
In your situation given you have all the veiwing stations and 95% of the gear required I would put a premiun on sales, Say 20% of all net sales then split the remaining net profit 50-50. Obviously you'd go 50-50 on all expenses papers inks etc. Which would leave a split of 60-40. That seems pretty fair. Given that you partner is a competant photographer. Yopu will be spiiting chips if you sell 90% of photos and he sells 10%. You might need to look at a form of remuneration relating to sales. It can get pretty ugly but the more easy going you are the less you will get payed.
Will be interesting to see what eventuates next time the games are on as I don't talk to one of the photogs anymore as he spat the dummy at me coming back to The Gold Coast and taking over what was my road bike track day photography business before I went around Australia for 12 months. Give a guy a leg up to an event untill I get back and when I get back I get very ordinary announcement posted on his website about me and my lack of morals ah well all is good now I have more events to shoot now than I did a year ago.
Here is a few links to some of my road bike trackday shots which explains why I got my trackdays back again
http://www.photo.net/photodb/photo?photo_id=2087803 http://www.photo.net/photodb/photo?photo_id=2087798 http://www.photo.net/photodb/photo?photo_id=2083393 http://www.photo.net/photodb/photo?photo_id=1352552